Leica M9:the digital M7?
Project '864' is the internal designation for the camera that is now known as the Leica M9. The number refers to the area of the 35mm negative with the classical dimensions of 24 x 36mm which equals to 864 square mm. When I was informed about the project I at first had the impression that the M9 was simply an M8 with a bigger sized sensor and basically this is the case. The hardware of the M9 is almost identical to that of the M8 with the exception of the 864-sensor, a Kodak CCD sensor with the same pixel pitch as the KAF-10500, employed in the M8 and M8.2. Superficially there are a number of changes in the body. The top cover has lost the display at the far left side, where you now find a shape reminiscent of the M7 and MP covers. The reasons for this change are twofold: the new anthracite color (replacing the classical silver chrome paint) would make the left part of the top cover top heavy in appearance when you use the normal M8 top cover shape. It is a small detail, but the anthracite painted cover would not look pleasant. The small shortening of the area of the left deck is a world of difference esthetically speaking. The other reason is a matter of bean counting. Dispensing of the display reduces manufacturing cost. Another example of cost cutting is the change of the sapphire cover glass for normal glass. M8.2 users might smile when reading this. The introduction of the bigger sensor did not change the finder magnification which stays at 0.68. It is not easy (even impossible) to integrate the classical finder of 0.72 into the slightly thicker body shape: the optical path is different. But the finder now covers a wider area and we see the re-introduction of the 135mm frame. The M7 offers the range: 28/90, 35/135 and 50/75. The M8 has 24/35, 28/90 and 50/75 (use in addition the 1.33 crop factor) and the new M9 has 28/90, 35/135 and 50/75. I made a number of tests with the Apo-Telyt-M 1:3.4/135 and the use of this lens is quite possible. To be really confident about the selected focus plane, the 1.4 magnifier is a must. Using two magnifiers is not an excessive or obsessive move, by the way. Remember too that the display does not offer an accurate representation of the true sharpness! Using 90mm and 135mm lenses on the M9 requires some care as the critical sharpness plane is much narrower than in the case of film emulsions where a certain depth does compensate small focus errors.
The shutter dial has lost the superfluous 'S' selection and gained a 8sec option on the vacant location. You can still select the Snapshot profile, but this is now done as a menu option. The most remarkable changes are indeed found on the software (interface) part of the equation. The 'Protect' button has changed into the much more useful 'ISO' button. Now it is possible to change the ISO setting directly from the camera. It is still not as fast and convenient as a physical dial, but it is a vast improvement over the previous cumbersome menu selection. The ISO choices are from ISO 80 (PULL) to ISO 2500, so no dramatic changes here. Noise seems to be reduced at the higher ISO settings. The PULL option is new, but in fact it operates as a constant over exposure setting: not really earth shattering, but nice to have sometimes.
More important are the inclusion of options that were long overdue and were standard features on even the most basic digital SLR camera. There is now a provision for bracketing with 3, 5 and 7 pictures over a range of +/- 2 stops in half stop increments, nice for the popular HDR picture style. The shutter keeps the discrete mode, introduced with the M8.2, but adds a SOFT option where the shutter is triggered immediately without locking the exposure setting.
A nice feature is the option to manually select the lens that is in use. The required upgrade of older (non-coded) lenses is gone: you select the lens from a list in the menu and the software records the focal length and some additional characteristics. Use AUTO when a coded lens is used and MANUAL when a non-coded lens is used.
You can now choose between silent mode or signal tones for a number of functions. Exposure compensation can be set permanently through menu options or on a per image basis by setting the dial: here you can choose between using the setting ring itself or a combination of shutter pressure and setting ring when you do not want to accidentally changing the exposure override. A three stops range is being offered. You now can organize your map structure on the memory card with the option of folder management.
Flash functions are identical to what is being implemented in the M8 series. The sensor has the same basic characteristics of the Kodak sensor built into the M8: the noise at higher ISO values is still unpleasantly high. The bigger sensor size delivers a file with a much larger size of course: 18 Million pixels is the basic number. But now you can select a new option: DNG uncompressed which creates files with a size of 34.7 MB capturing the full potential of the sensor. The internal dynamic compression to 8 bits is then overruled. With such large files, the speed of the recording is lower and the battery drain is higher. I used the DNG uncompressed file size on a San Disk 16 Meg card and ran out of power (fully loaded battery) after a mere hundred pictures taken on one day. This may not be typical, but it is recommended to add a second battery to your bag when doing extended day long shooting.
M8 and M8.2
These models are discontinued and might become known to Leica historians as the Leica camera models with the shortest life cycle, with the possible exception of the M6 HM model. Especially the M8.2 has had an effective production life cycle of just one year (from summer 2008 (Photokina 2008) to summer 2009 (introduction M9)). You can still make excellent images with these cameras and any M8/M8.2 owner should carefully consider the options before deciding to buy the M9. The distinguishing mark of the M8/M8.2 models is the required use of the IR filters to cut off the excess infrared radiation from being captured by the sensor. Leica cited that the very thin cover glass of the sensor was required to compensate for the short back focus of the M lenses in combination with the steep angle of the rays at the edges of the field. That was also the main reason for the adoption of the smaller sensor. The M8 camera versions can be interpreted as a bridging act between the M7/MP and the future digital versions of the M line. In the evolution of the M line the M8 is a necessary step, and required for learning the engineering and software requirements for solid-state cameras. But as biology dictates the environment changes and then you have to adapt or die. Does this imply that the M8 buyer has been used as money and experience suppliers for the Leica R&D department. In a sense this question has to be answered affirmative, but we may with some justification also state that the Leica community is used to small evolutionary steps and is very quality conscious. In 2006 the M9 would be impossible to manufacture and to be honest I like the M8 sensor size as it forces me to be very critical about scene selection and composition.
The new sensor has the same pixel pitch as the previous one, which implies that the Nyquist limit of resolution has not changed. The bigger area does accommodate the full angle of view of all Leica M lenses. Technical changes in the sensor design have solved the IR problem (the IR filters are no longer required), but the performance at the edges of the image, especially with wide angle lenses might be not as good as is sometimes claimed.
The differences are quite small and may be due to the statistical variations, which always create a margin when testing lenses and equipment. The image quality of the M9 pictures could be improved when you take advantage of the bigger sensor area: you can get closer to the scene to capture the same angle and this helps in the recording of fine detail. When the M8 is used expertly and within its limits of angle of view, the image quality is very close to that what you get with the M9. In this sense the M8 is not obsolete. The larger sensor and the increased number of pixels helps you to capture the same scene area with more pixels to record the details and this automatically improves the definition of fine detail.
An in-depth comparison between M8, M9 and M7 will be published in the following part of this review.
The M9 in use
The last month (august) I have been shooting exclusively Kodachrome in my M7. In comparison I used the M9 with the same lens. The switch between the two worlds is completely seamless and the intuitive operation of both cameras is exemplary. The M7 is very basic and requires a lot of pre-photography preparation when additional functions are needed, like exposure bracketing. But then the core act of the M7 is the anticipation and preparation of the shoot and the fire-only-one-bullet approach. The M9 offers more options, changing ISO on the fly, changing the exposure bias where required, do exposure bracketing when insecure of the right choice, use the continuous shooting option (up to seven pictures when using DNG uncompressed) to capture the right moment. This list shows what the M9 offers compared to the M7: more options, more flexibility, more influence on the picture captures conditions. The danger is also visible: the subtle shift from the photographer being in command of the picture and the camera software in command of the image. The M9 can accommodate all Leica M lenses from 16mm to 135mm with the inherent and intended focal length. Once you have created your own profile in the camera, the M9 is as simple to use as an M3. This is in my view the strong point of the M9 and worth a congratulation to the Leica designers and engineers. The M9 is the only digital 35mm camera that operates and feels like a classical film loading camera.
The significance of the M9
The M9 is a mature product that can command a serious role in the 20+ megapixel-35mm-style-camera league. The pixel pitch of 6.8 micron allows excellent definition up to 70 line-pairs/mm, which is enough for really crisp prints in A3 format. The list of features of the M9 will satisfy any user who wants that traditional elegancy of use that Leica is famous for. On the other hand the scope of the feature list can convince users who want to adapt the working of the camera to specific profiles based on programmable camera functions. Luckily Leica resisted the temptation to overburden the camera with an endless array of goodies no one can find good use for, from a photographical perspective.
Any M7 user will feel at home and at ease with the M9 and can master the camera within a few hours of reading the book and exploring the camera functions. To get the best of both worlds, one needs an M7 for the fully chemical workflow and an M9 for the fully digital workflow. The Leica lenses can be switched between both cameras with the same basic optical performance and angle of view.The M9 motorized transport operates rather slowly and the buffer is not large. But the speed of operation is faster than what an experienced user can accomplish with the mechanical trigger mechanism of the filmloading M-cameras. I personally find the focus on the highest possible number of pictures per second a bit overhyped. For sports photography it may be an important factor in the choice equation. For a manual focusing CRF camera the speed of the motordrive is less relevant and in itself the speed of the M9 (and the M8!) is quite good. And Leica photography is about selecting the moment, not firing at will in the hope that you catch a moment.If you were looking for radically new features in the M9, you might be disappointed. The camera has the full DNA of the classical Leica CRF and is still completely locked in the M-evolutionary tree. You can improve a camera to a certain level and to the limit of its natural habitat. The M9 represents the final stage of the classical CRF concept for the digital workflow. Some refinements will of course always be possible. A radically new version would require a substantial and fundamental change in the DNA make-up. This then is the significance of the M9. Overall you can sense that the Leica engineers and developers are becoming more in synch and at ease with the demands and possibilities of digital technology without losing sight at the fundamental Leica characteristics as elegance, simplicity and performance. Do I hear someone muttering about the new Mac operating system, Snow Leopard, which has a comparable approach? The Leica M9 is a sensible mix of traditional Leica virtues and state-of-the-art camera features. It is a tool for Leica aficionados who still think chemical, but want to work with a digital workflow.
Next part: the performance of the sensor with wide angle lenses.
The M9 landed in the Leica sphere with a bang. As is usual with splashes, they calm down quite soon. And then we have time to reflect on the long term impact and significance of the M9. Historically the introduction of the M3 can be seen as offering the closest parallel. In those days we did not have the internet rumor machines and blogosphere. The birth and development of the M3 was only known to a small group of persons. The only information channels were the printed press and the photo magazines. The pace of innovation was much more relaxed and one could take the time to think and reflect on important issues and themes. The Leica M3 offered un unprecedented ease of use, the highest level of precision engineering in photography and the best lenses. This package did boost the quality and immediacy of documentary photography and for a brief period of time the M3 was the most valued camera model in the world.
Switching from a fifty-year-old M3 to a two-weeks old M9 does not force upon the user a paradigm shift in handling and concept. In fact the newest branch on the evolutionary Leica tree is an M7 with a digital core. And the M7 is the M6 with a core of automation and the M6 is an M4 with an inbuilt-exposure meter. And the M4 is an M3 with upgraded finder. This sketch of the Leica M lineage is anathema for Leica historians who attach prime importance to small engineering differences, but for the attempt to locate the M9 in the Leica world, it will suffice.
The Leica M9 will presumably not have a comparable impact as the M3 had. The world of photography is too different now. And the world of engineering and manufacturing has changed too. Many camera historians will claim that a Zeiss Contarex, a Leica M3, a Nikon F and a Canon F1 represent the pinnacle of mechanical engineering sophistication. Compared to, for example some current MicroFourThirds models, the cameras mentioned above, appear to be rather crude in design and construction. The Leica M9 stands firmly in the classical precision engineering philosophy. That is the strength, but also a weakness especially when we want to look at the future developments. I will return to this theme at the end of the M9 report, but for now I will look at the capabilities of the M9 as they are.
The IR issue
The coupling of a solid state sensor in the M camera body with the Leica lenses with the typical short back focal distance of 27.80 mm posed big problems for Leica designers. Many digital camera systems employed several layers of filters in front of the sensitive pixel surface to cure problems of moire and resolution, resulting in a filter thickness of up to 4 mm. This is a hefty thickness and will certainly have an effect on image quality. The steep angle of incidence of the rays at the edges of the frame will interfere with the thickness of the filters and result in increased shading and color shifts and reduced definition. Given the state of the art, Leica decided to focus on a layer as thin as possible to improve image quality. The consequence of this decision was a reduced sensor size and an increased IR sensitivity of the M8 series of cameras. An additional IR filter on the lens effectively solved the IR problem, but is not the most elegant solution imageable.
I used a test chart specifically designed to show IR color casts and tested the M8 with and without a filter, the M9 and as comparison the Nikon D3x, the current camera of reference in the high end camera market. The M9 filter thickness is now 0.8mm as compared to 0.5mm for the M8 and more than 2mm for the D3x. The Nikon cover glass incorporates a lowpass filter that the Leica lacks. Leica claims that the solution in the M9 improves definition of fine detail. The occasional occurrence of Moire effects are filtered by the software. This applies only to the JPG images, which you often do not want to use because of the internal processing that is not always as good or flexible as the best RAW developers support. Here we find the classical difference between lab processing and your own darkroom processing.
Again we may refer to the classical wisdom of AgX times: a big format with a moderate lens may give better results than a small format with an excellent lens.
The definition of the sensor.
The M9 sensor has pixels with a size of 6.8 micron and the Nikon D3x has a pixel size of 5.9 micron. Theoretically the Nikon has a small edge in ultimate resolution, but we should again return to old wisdom and note that there is no substitute for size (a bigger capture area or negative is always a definitive advantage) and a better lens can offset a bigger capture area to a certain extent. A CRF camera has additional aspects to look at to for optimum performance. The camera lens must have the exact distance from lens flange to sensor location, the rangefinder must be adjusted to this distance too and the focus cam must be precisely machined with the correct steepness over the whole focusing range. Leica sets the nominal distance between flange and sensor location to 27.80 mm. I checked three lenses (3.8/24, 1.4/35 and 1.4/50) and got these values: 27.84, 27.83 and 27.81! This is an outstandingly good result and a fine indication of the care of production at the Leica factory. There is an age old rule that states that with smaller apertures the accuracy of focusing can be relaxed as the extended depth of field will compensate for focusing errors. I will explain in a parallel article that the introduction of the M9 forces one to rethink the classical testing paradigm, but here I will look at two aspects. I did a rather exhaustive analysis of the focusing accuracy of the M9 with the 1.4/35 asph (assuming that this lens will take a prominent place on the M9 because of its classical focal length). I placed the M9 in front of the familiar test chart (the nine star charts in three rows of three columns) at a distance of 1.35meter. I again assume that the Leica user will exploit the format size to its optimum and will get as close to the scene as possible. At closer distances the focusing accuracy is more critical. I made a range of eleven exposures with through focus steps of 1 cm (from 1.30 to 1.40) on the tripod. One range at full aperture and one range at aperture f/2.8, where one would assume to have some latitude in focusing errors. Then I evaluated every star in the center with the Imatest analysis program and selected the best result. With maximum aperture the result is amazing: the zero position delivers the best result. Note that both extremes are less good The plus range gives generally the better performance: so it is best to focus a bit farther than indicated. With the aperture stopped down to f/2.8 the best position is the +2 focus: here we see in critical situations the effect of a slight focus shift. But it is also evident that even at 2.8 there is hardly room for focusing errors if the optimum performance is required The accuracy of the rangefinder of the M9 is beyond reproach, but the optional magnifier (1.4x) is absolutely necessary. This exercise was repeated for the Nikon D3x (not shown here) and the best focus position on both cameras at 1.4 and 2.8 was registered. Then the same test-chart were shot and the result now evaluated for maximum definition and resolution.
To study the effect of sharpening in post processing I used Capture One with sharpening at zero and 100%.Note that the result of the sharpening process is to enhance the contrast of the low and medium frequencies and has hardly any effect on the critical high frequencies. We may infer from these graphs that the Nikon images benefit more from the post processing, but get that now familiar (and not always pleaseant) digital look, where the Leica images are more closely related to the classical film look and here the sharpening effect is less pronounced. The Leica M9 is quite close to The Nikon D3x in definition and resolution, but Nikon photographers do not need to fear that the M9 will dethrone the D3x as the reference camera for state of the art quality. Stunning as the M9 pictures are, they must be put in context and then the Nikon D3x images are just better.
Leica M9,definition M9 versus M8 and D3x.
There is a valid question to ask about the Leica M9 tests in general. The final photograph (on print preferably or on the screen) is the result of a chain of processing steps. Specifically you cannot test a sensor in a camera without a lens attached to the body. In fact you can never make statements about the sensor quality or performance without reference to the lens attached. This is not a new observation: in the days of AgX emulsions film was tested with a lens on the camera. And everyone was aware or could be aware of the fact that lens and film had a cascading relationship: when the lens had a quality factor of 0.7 and the film had a QF of 0.9 the resulting image could have a maximum of 0.6 of the theoretical optimum. Film emulsions could be tested without a lens (with a grid or a knife edge directly placed on the emulsion) and one could get resolution or MTF figures in a stand-alone fashion. For lenses the same approach worked: you can measure the MTF or other properties of a lens without using film.
In the current digital world this approach does not work anymore. The interaction between sensor and lens is much more complex and multi-facetted than can be inferred form the rather crude but ubiquitous LP/PH figures. It is too simple to look at the sensor data and find that there are, let us say, 4000 (wide) by 2000 (high) pixels on the sensor matrix and then to divide this number by 2 and infer that the maximum resolution is 1000 linepairs for this picture (sensor height). This number is also referred to as the Nyquist limit or limiting frequency. You need a minimum of two pixels to record two lines with different luminance to see a line edge. To be more precise we have to say that sampling in the spatial domain only refers to edges: an edge in the spatial domain is the equivalent of the sinusoidal shape in the temporal (audio) domain. Just counting LP/PH is the same approach as looking at resolution figures that was so popular in the sixties and seventies of the previous century.
The Nyquist rule is properly identified as the Shannon or Nyquist sampling theorem. The sampling theorem indicates that a continuous signal can be properly sampled, only if it does not contain frequency components above one-half of the sampling rate. For instance, a sampling rate of 2,000 samples/second requires the analog signal to be composed of frequencies below 1000 cycles/second. If frequencies above this limit are present in the signal, they will be aliased to frequencies between 0 and 1000 cycles/second, combining with whatever information that was legitimately there.
The Leica M9 sensor has 145 pixel rows per mm or 6.8/6.9 micron per pixel. The number of pixel rows is equivalent to the sampling frequency. The Nyquist theorem tells you that the analog (optical) signal must have frequencies below 73 c/mm to be properly sampled. That is the reason why most camera sensors use a low pass filter to cut off all optical signals above this frequency. A low pass filter does not have a sharp cut off but a gradual suppression of high frequencies. And many lenses can record frequencies above 70 lp/mm. The quality of the edge will be influenced by all these aspects. Not unlike the quality of the grain in an emulsion is more important than the mere number of grains per square mm. Instead of counting number of lines it would be better to study the quality of the line edge!
Schneider and others have demonstrated that the simple rule that two pixels will suffice for the recording of a pair of black and white bars (a line) only applies in the case the thickness of the bars is identical to the pixel pitch and match completely. This condition is not often found in practice and then we may need three or more pixel rows to record an edge. To follow the question stated at the beginning one would ideally one like to select a lens that has a limiting frequency equal to what is required by the Nyquist sampling theorem. Many Leica lenses can resolve more than 80 lp/mm and these would be aliased to frequencies below 70 c/mm and influence the quality of the edge.
These aspects are unavoidable and more study is needed to look at the detailed reproduction of the edges. For the moment the best one can do is to select a lens with very good definition that is representative of the performance of the Leica lens range. Results that are presented should always be interpreted as system results of the cascading of lens/sensor/in-camera image processing.
The systems that are analysed in this report of the M9 (the M9, M8 and D3X) are all high grade systems and it is not easy to make general statements. There is a tendency, sometimes an imperative to make statements about the best system, where 'best' is interpreted in maximum number of LP/PH or some other quantifiable parameter. It is evident that the M8 (as example) will not score very high marks in this discipline because of its smaller sized sensor. The practical examples below will show that the M8 will resolve less detail than the other two cameras. It cannot be the case however, that a camera that a few months ago was characterized as producing outstandingly good imagery now is ripe for the dustbin. This attitude would imply that a car that has a top speed of 100 m/h would be useless when a new model arrives on the market with a top speed of 120 m/h.
The current behavior of looking at image files at 100+% on a computer screen and study individual pixels has aptly been called pixel peeking and has hardly anything to do with appreciating or evaluating photographs or pictures. You did not study grain patterns under the microscope in AgX days, did you? And in the AgX period there were films with different grain size and resolution. Microfilms record a stunning amount of detail, but you can hardly see it unless at unpractically large prints. When using normally sized prints in A4 or A3 format many recorded details cannot be printed and are factually invisible. Pixel peeking at 100% on the screen is the equivalent of grain viewing under the microscope. But is not the same as creating prints for appreciative viewing. We should never forget to ask what we can effectively see in print and what we want to record in print. This is obviously not the same. Some common sense and sanity is certainly needed in the digital domain. The same is true with the M8 and M9 pair. The M9 would represent a microfilm approach in AgX terms and the M8 a 100/400 ISO film.
The pictures are processed by Capture One with very moderate sharpness parameters and no adjustment of color or exposure. The export was a large TIFF file, selections were made and converted to JPG for web-use. There is some quality-loss compared to the original TIFF files, but these are too big for web-use. The top left corner of the D3X picture.shows that the quality is very high, with accurate colors, good definition and no artifacts. The same selection from the M9 picture shows that the quality is comparable as far as definition goes, but Moire artifacts are clearly visible and color shift is present too. The M8 picture at the original scale shows that the quality is high with quite good color, moderate definition and no artifacts. The same picture, but now scaled to 133% to get the same size as the original M9 image shows no improvements of course, but the differences are now more clearly visible. Especially the lower contrast of the M8 image is remarkable. At the introduction of the M8 Leica claimed that the smaller sensor size was necessary to take account of the short back focal length and the steep angle of the oblique rays. The M9 improvements are impressive, but the comparison with the D3X images shows that even with a low pass filter and a thick system of cover glass in front of the sensor Nikon engineers can deliver first class imagery at least comparable with the M9 performance. The Moire artifacts of the M9 are peculiar while the M8 is free from these artifacts.
Below is a picture from the center of the image. This part of the test image is the Esser test chart for the comparison of difficult and accurate skin tones. But you can also look for sharpness details in the hair.
The D3X picture is below. Sharpness is excellent and color reproduction is very good. There is a slight over exposure.
Then the M9 picture. Sharpness is slightly lower and the skin tones less accurate. But the high lights are better preserved, which could be attributed to a high dynamie.
Below is the M8 picture. Color reproduction is close to the Nikon example. But overall the quality is good, but it lacks the bite of the other cameras.
The M9 has joined the top class of 35mm sized sensors, but with some caveats. The artifacts may not be visible on all occasions, but show that Leica should do some additional home work in this area. The smaller sensor size is not a drawback when coupled with the excellent Leica lenses, but the absence of the low pass filter does not bring any truly competitive advantages. The M9 pictures are not better than the comparable Nikon pictures, but presumably at this stage of the evolution one could not ask for more. The M9 user does not have to entertain any inferiority feelings, but a realistic assessment of strengths and weaknesses is not a bad thing. In the course of this series we will look at other aspects of the M9.
M8 versus M9.
The comparison in relative and absolute terms between the performance of the M8 and M9 will command much space in print and discussion among Leica aficionados. In the series of pictures discussed in this article the M8 came out on third place which is no surprise, but a bad result it is certainly not. In the tests the full size of the frame was exploited and this means that the M9 can be put closer to the scene with the same angle of view but a bigger enlargement allowing more pixels to be used for the same scene detail area. This is a bit unfair, as if you were comparing a half frame (PEN) camera with a full frame (M) camera (in classical analog terms). This theoretical disadvantage of the small Leica negative was already noticed by the early Leica pioneers when comparing Leica enlargements with 6x9cm contact prints. Their solution was the rule to get as close as possible to the scene so that there was no cropping necessary when enlarging and every precious grain clump could be used for the print. So I set up the M8 in front of the test chart and chose a distance that fills the sensor area with the total area of the test pattern. Then I kept the distance, used the same lens and now the M9 was on the tripod. Because of its bigger sensor, the area of the test pattern does not fill the sensor area but only the center portion. This center portion has the same dimensions as in the M8. The lens is identical, the distance too, so the enlargement factor is the same and the pixel pitch of both sensors is also the same. If you crop the M9 image to the dimensions of the M8, you have two identical pictures in scale and area. These pictures (M9 cropped and M8 full size) show the test patterns on the same scale and with identical pixel dimensions. The pixel pitch of 6.8 microns does not change between the M8 and M9.
Compared to the D3X we might even state that the M9 tends in its image qualities to a analog representation while the Nikon has a more digital representation. For Leica cross overs this behavior is very pleasant. And non-Leica migrants might see favor in this combination of film like properties and excellent optical performance.
These figures demonstrate that the M8 can capture the same level of definition as the M9 when both pictures have the same scale and magnification. With other words, if you do not exploit the 1.33 factor of the bigger M9 sensor to the full, then the M8 might be as good as the M9. Of course the M9 has a higher potential for bigger enlargements, but if you restrict yourself to high quality A4 prints, then the M8 is a good alternative to the M9. I have expanded on this topic as I got numerous questions from readers who are concerned about the status and future use of the M8 in the light of the boosted expectations around the M9. As can be seen in this part of the report, the M9 is without doubt a big step forward compared to the M8, at least performance-wise, but that does not imply that the M8 is not a formidable picture machine. It has to be stressed that the current attitude of pixel peeking is detrimental to the pleasure and appreciation of real photographic prints, where many of the characteristics that are visible on screen, are not detectible in print. A case in point is the occurrence of chromatic aberration (the red or blue bands next to black/white transitions) which is clearly visible on screen, but not visible in prints with lower magnification or in black/white images. The classical approach to lens design has always been to focus on those properties that are visually important on the print or in projection. That is why the limit of 40 lp/mm has been selected as relevant for photographic purposes. In my current blog I have argued that this paradigm needs to be adapted to current practices and demands. But one should not overshoot the case.
Leica M9, part 4, vignetting and automatic shading reduction.
Some readers said it was unfair to compare the Nikon D3X with the Leica M9 as the Nikon is bulky, very feature-rich and has a totally different handling. The M9 on the other hand is compact and intuitive to use and should be compared to a camera in its own league. Let me note again (I said it in the review, but repetition is sometimes welcome), that I did not want to compare the Nikon asa camera system to the Leica as a camera system. It did a review with this goal some time ago and do not wish to repeat this story. I used the Nikon as it is universally acclaimed, like it or not, as the benchmark and point of reference for image quality and performance in the high-end professional digital camera market. There are camera systems with more and with less performance, but the benchmark is just this: a point of reference. Some readers got the impression that I favored the deployment of AA filters or low pass filters. I do not. I think the Leica approach is inherently the better option, the less thickness of the cover glass the better! What I noted is the effectiveness of the Nikon low pass filter in combination with the post processing software inside the camera. While the Leica option is theoretically sound, in direct comparison with the D3X one has to conclude that at this moment in time the true potential of the thin cover glass strategy of Leica can be improved to get an decisive edge compared to the main rivals in the high-end professional 35mm market.
A comparison between the M9 and comparable cameras is quite difficult as there are none! I am not aware of a current digital CRF with a sensor that can be compared to the M9 sensor. I do not consider the MFT models for Olympus and Panasonic valid competitors to the M9. The only candidate is the Leica M8 and M8.2 and I have compared these models with the M9. Some readers did comment that the advantages of the M9 are not big enough to warrant a migration from the M8 to the M9, because their demands are fully satisfied with the M8. I try to give a balanced analysis of the virtues and possibilities of both cameras and I fully agree that the potential capabilities of the M8 in expert hands can comply with many user demands in normal practice. But the M9 has additional advantages that may convince M8 and non-M8 users to buy and use this camera. There is a second approach to compare M8 and M9. In the previous part I used the same lens and distance and thus did not exploit the M9 sensor size to best advantage. I neglected on purpose the classical Leica rule to fill the negative size with the maximum amount of information.
The M8 has a crop factor (better is the reduction of angle of view) of 1.33 and it is common practice for Leica users to use a 35mm on the M8 to compare with the 50mm on film-loading Leica bodies. It is interesting to make the same comparison with the M9. So I put the SX 50 asph on the M9 and the SX35 asph on the M8 and made the same pictures on tripod at the same distance. The exposure meter was on A as was the white balance. I did not correct for color bias as this is not my goal here. Both lenses were stopped down to the optimum aperture of f/4.
Below you see a smaller image of the full size digital negative. Note that the M8 image is smaller but has only a minute amount of detail loss
The M9 images show a higher level of definition and a crisper reproduction of very fine detail. It is up to the reader to decide whether this advantage is worth the upgrade or even a first buy into the digital M world. I got many queries from readers who are actively involved in AgX photography with M7, M6 and/or MP and are now wondering whether the moment has come to make the transition. I will devote a future part of this report to answer this question, but as a start I can say that the M9 pictures are very close to and may even surpass the quality of the best of the modern medium speed films of ISO 100 to 125.
Shading is also known as vignetting. One of the main arguments of Leica for the smaller M8 sensor was precisely the additional vignetting that was introduced by the combination of the steep ray angles at the exit pupil and the shape and position of the micro lenses on the individual pixels of the sensor. The M9 sensor has to cope with the same ray angles but has an optimized micro lens shape.
In addition Leica has incorporated software in the camera that can reduce the amount of vignetting. This technique is not new: many post-processing programs have this option. In the Leica M9 you can select the lens used manually and this also offers third party lenses the same luxury. Of course the corrections are optimized for the Leica lenses, but many third party lenses share a comparable optical design and might benefit form the correction. As a matter of interest we can note that in many cases vignetting or shading is not a big problem. The eye can easily accommodate and ignore moderate vignetting as long as the transition is smooth from center to corner and below 1.5 stops. Measurements of shading often report figures of 1 stop and more and most readers assume this to be a problem. But shading becomes troublesome only above 1.5 stops and should not be overrated. The Leica M9 can handle oblique rays as long as the angle at the exit pupil is below 35 to 40 degrees. Above this angle the shading cannot be compensated. That is the reason why classical lenses like the Angulon class will exhibit significant vignetting.
But shading in digital cameras also implies color shading. As the rays of light have to pass obliquely through a cover glass of some thickness, the length of the path of travel increases and so does the color shift with some loss of the red light, increasing the cyan part. In most cases this is not detectible, but it can be noticed in critical conditions.
It is also worth noting that the same amount of measured vignetting will be less noticeable on film than on the sensor.
The main question however is how effective the on-board shading compensation is in the M9. I used a dedicated piece of equipment with extremely uniform luminance distribution and checked the amount of vignetting with and without the M9 lens detection on OFF and Manual (where appropriate) of AUTO. Generally one may say that the results are quite good, with an improvement of between a half and a full stop. In extreme cases the vignetting is not gone completely but reduced to minor proportions.Note too that the shading algorithms also correct the color shift. This is quite visible with the E24/3.8
There is considerable interest in the behavior of the Zeiss ZM lenses on the M9 with the lens detection on Manual selection.
I checked the following range of ZM lenses.
ZM 2.8/35; ZM 2.8/28; ZM 2.8/25; ZM ZM 2.8/21; ZM 4.5/21; ZM 4/18; ZM 2.8/15.
With the exception of the 4.5/21 which showed significant vignetting all ZM lenses improved when the lens selector was on the comparable Leica lens. This is no surprise as many ZM and L lenses have a comparable optical design and then should react to the same correction with the same behavior. With the ZM 15 you need to experiment a bit with different settings to get the best result. It is advisable to use this approach to the other lenses too. Generally we may conclude that almost the full range of ZM lenses is useable on the M( with good results as far as shading goes. I had no access to Voigtlander lenses, but this experience shows that it is worth a try, but results may differ significantly.
In the next part I will look at ISO speed and noise and some other topics.
Leica M9, part 5, noise and dynamic range.
For this test I used the OECF noise chart with 20 patches covering a 10.000:1 luminance range. This is the industry standard. The luminance range corresponds to a range of more than 13 stops. The graphs I will present are mathematical analyses of the image files, made at different ISO values. They may look a bit intimidating at first glance, so here is a short explanation. OECF stands for Opto-Electronic Conversion Function and is widely regarded as the best determinant for dynamic range analysis.The top left graph (the string of grey squares) on the image is this OECF and it may be interpreted as the classical density (characteristic) curve of a film emulsion, starting with a low density (shadow) at the bottom left corner and ending with a high density (highlight) at the top right corner. Films follow the well-known S-shaped curve and you see this shape again in the graph. The bottom graph represents the noise level, in the same way as grain size was measured in the AgX world. In the digital world the Signal to Noise Ratio is the best known parameter, denoted as SNR. This parameter is measured in dB and the formula is SNR = 20 x Log (10) (Vs/Vn). The practical range goes from zero to 60 dB, with the value of 20 dB as the watershed value; higher values go from acceptable to excellent and lower values go from not acceptable to awful.
This scale is not the same in all graphs but is dynamically and logarithmically adjusted. The yellow horizontal bar in the middle graph represents the noise level where good quality images start.
The figures on the top right side of the set of graphs shoe the dynamic range in maximum values and for different quality levels. As example: the D3X at ISO2500 has a maximum dynamic range of 13 stops, but this is theory. Several patches have the same density and are indistinguishable. This is the same situation as with film where we can have a very high density that cannot be brought to print with just noticeable luminance differences. This state of affairs is the reason why Ansel Adams, designing the Zone System, restricted the range to ten zones, each one just measurable and visually different from the next one.
The D3X at ISO2500 can deliver high quality imagery when the number of zones is limited to 5.6 stops, close to what a good slide film can handle. When a lower quality can be accepted the D3X can cope with ten stops or the full range of the Zone System. In itself not a bad result, but one to accept with restrictions.
The cameras were all set for manual white balance to correspond with the color temperature of the test equipment. Note that the Nikon and M8 have excellent grey values, where the M9 is blue biased. In this area Leica needs to do some additional home work. I did not adjust the color balance as this is not the goal of this part of the range of M9 articles. For the record: the source light has a Kelvin value of K5000 and all three cameras were manually set to this value. A check with Capture One to see if the cameras recorded this source to correct values gave this result
D3X set to K5000, recorded as K5000
M8 set to K5000, recorded as K5000
M9, set to K5000, recorded as K5450
ISO 160 on D3X, M9 and M8
The D3X has a useful dynamic range of ten stops and an SNR of on average dB 47. The M8 has a useful dynamic range of eight stops and an SNR of on average dB 47. The M9 has a useful dynamic range of seven stops and an SNR of on average dB 43.5. The M9 is remarkably somewhat less good than the M8.2 I used. The differences are small however, but visually present. The Nikon is not better and this is surprising as the Nikon D3x has been championed as a speed king. But at lower ISO values this advantage is not clearly visible.
The D3X has a useful dynamic range of ten stops (but for maximum quality the range is only 6 stops) and an SNR value of on average dB 47. The M8 has a useful dynamic range of eight stops (for maximum quality it is six stops) and an SNR of on average dB 46, almost equal to that of the Nikon camera. The M9 has a useful dynamic range of seven stops (for maximum quality it is six stops) and an SNR of on average dB 43, which is lower than that of the other two cameras, but not by much. I cannot help but warning that to attach too much value to small numerical differences is as dangerous as relying too much on subjective visual interpretation. I have always been skeptical of the many magazines that rank cameras and lenses in percentage points: a camera/lens combo with 73% is always better than a camera/lens combo that scores 72%. This is nonsense! The D3X has a useful dynamic range of ten stops (but for maximum quality the range is just below 6 stops) and an SNR value of dB 42 on average. The M8 has a useful dynamic range of eight stops (for maximum quality it is just below six stops) and an SNR of on average dB 43 a slightly better result than that of the Nikon camera. The M9 has a useful dynamic range of seven stops (for maximum quality it is just below 6 stops) and an SNR of on average dB 41, just below the level of the other two cameras. The consistent result by now is that the D3X is best, closely followed by the M8 and the M9 is always a bit behind the M8.
ISO 1250 on D3X, M9 and M8.
The D3X has a useful dynamic range of ten stops (but for maximum quality the range is just below 6 stops) and an SNR of on average dB 45. The M8 has a useful dynamic range of eight stops (for maximum quality it is just above 4 stops!) and an SNR of on average dB 40, below that of the Nikon camera. The M9 has a useful dynamic range of seven stops (for maximum quality it is just below 4 stops) and an SNR of on average dB 39 which is below the level of the other two cameras. From now on the Nikon camera forges ahead with the ISO speeds and noise reduction. The D3X has a useful dynamic range of ten stops (but for maximum quality the range is just below 6 stops) and an SNR of on average dB 40. The M8 has a useful dynamic range of six and a half stops (for maximum quality it is just above 3 stops!) and an SNR of on average dB 36, below that of the Nikon camera. The M9 has equal values.
It is clear that the Nikon has the edge, a small one up to ISO 320, a bigger one up to ISO 640 and a major one from ISO 1250. The ISO 2500 is not really useable on the Leica M8/9 camera, but as a last desperate resort is is an option. There is a persistent tendency to hype up the performance of the Nikon high end digital SLR cameras as far as noise and dynamic range at higher ISO values is concerned. This is true above ISO 1250, but at lower values the competitive advantage compared to the Leica M8/9 is not very pronounced, al be it visible. For me an excellent ISO 400 setting is a great improvement. just now that Kodak has released the very good T-Max 400 film. Generally one may note that for best quality at higher ISO values a dynamic range of four to five stops is not a formidable achievement. It is interesting to reflect on the fact that the M8 performance is just ahead of the M9 performance. Differences are not impressive, but just there. The final result that the M8/9 can keep up with the formidable Nikon up to ISO400 (to be really critical) is a pleasant surprise. Of course one can comment that the Japanese high end dSLR cameras are excellent up to ISO3200 (with the appropriate post processing), but I am happy with a very good ISO 400 and excellent wide aperture lenses. This combination is well suited for the goal of emulating high quality reportage and documentary photography in film-look-alike. And that is what Leica is famous for.
Leica M9, part 6, intermezzo.
Before concluding this series with an analysis of the color reproduction capabilities and the comparison with film (Tmax100 and Spur Orthopan microfilm) it may be a good idea to pause for a moment and reflect on the more philosophical aspects of the M9 in the Leica lineage.
There is a strong connection between music and photography as both are based on the physics of the wave phenomenon. Waves generated by instruments in a temporal or sequential mode produce the sounds we hear and like. Sound wave share the same characteristics (period, frequency and amplitude) with optical waves. Light energy falls on a subject and the energy is bounced off the surface and the resulting waves fall on the eye as receptor in a spatial mode (static image) or a spatial/temporal mode (moving images).
The correspondence between music and photography is not only evident on the physical level, but also on the aesthetic level. The words to describe a piece of music are almost identical to the ones we use in photography like tonality, harmony, timbre (tone color). We know that a visual edge is made of of a superposition of high frequencies and the same is true of a musical sharp edge. The famous discussion whether a CD has a better sound than an LP is copied in the photographic discussion about film based and sensor based receptor technology. There is a slight revival of LP discs, and the LP engineers can easily explain the difference between the CD and LP. The LP cannot record the high frequencies as well as the CD does and this results in a warmer sound that many listeners appreciate. The same is true when looking at the film based images: the high frequencies are reduced due to scatter and grain and the edges are slightly smoother and this is pleasant to the eye which dislikes sharp transitions. The digitally captured and manipulated image can retain the high frequencies resulting in sharp edges which are so pronounced in images as to be unpleasant. The eye will eventually adjust to these characteristics we may assume.
In the musical world we find a wide range of musical instruments, each one capable of a unique sound with a limited tonal range and timbre. The manufacture of musical instruments is often a mind-bogglingly complex business, subject to scientific analysis to be true, but in the end it is the master craftsman who has to do the job.
When reflecting on the status and role of the Leica M9 in the current imaging world (would one still dare to use the word ‘photography’?) I was thinking about the analogy with music and musical instruments. I was (accidentally?) listening to Beethoven’s Ninth Symphony, also called ‘The Ode to Joy’. The Ninth is part mystery, part masterpiece and this would be a fitting description of the Leica M9 too.
The virtue of the M9 is to allow CRF-users the benefits of the high-end digital workflow in combination with the basic attributes of the CRF concept as developed by Leica, in particular the classic viewing angles of the Leica lens scuderia. The M9 performance positions the camera in the top segment of the 35mm format dSLRs, and this guarantees high quality, studio-like imagery. The M9 does not however directly challenge the medium format digital backs and cameras in the same way that the AgX Leicas were no direct competition for the Hasselblad images and the 8x10 inch loading field cameras. On the other hand we may also conclude that the performance is in many cases close to what the Leica S2 has to offer. The reference to the musical scene is quite apt. No musical instrument offers the full range of tones that the ear can cope with and clearly a violin has its role to play next to a flute or a piano.
The M9 is a masterpiece by keeping all the classical CRF virtues and adding the ease of use of the digital workflow while not intruding into the mental workings of the photographer’s eye. Current dSLRs of Canon and Nikon calibre are closer to a Moogh synthesizer than to a classical instrument (to stay within the music analogy). Here starts the mystery of the M-series. Basically the CRF concept has to be considered obsolete technology since about 1970 when the SLR screens matured and the concept was dealt a final blow with the coming of age of the AF technology around 1995. The concept and the Leica embodiment of it has proven so strong that it still today has its band of followers who create pictures that forcefully connect to the core emotions of artistic vision. But just as Beethoven’s Ninth, there is an end to creative genius and the emergence of discussions about an M10 is a bit premature as the range of options is beginning to become exhausted within the CRF concept.
Geoffrey Crawley in his review of the Leica M5 called the Leica M a bottle of pure fresh water in a Pepsi Cola world. This conclusion is still viable in the current digital imaging world. The Leica M9 (and to be inclusive the M8 too), is the only camera for the digital workflow that is fully linked to the classical way of taking pictures.
The current obsession with ‘clean’ images (without vignetting, noise or grain) and extended dynamic range is a remarkable departure from the technical tradition in photography. It is a bit artificial too. All great images in photographic culture exhibit some grain and many also have a shade of vignetting. One might say that these properties define the proper characteristic of a true photograph. And Ansel Adams found that a range of six to seven stops with clear nuances within this tonal scale is all you need for very high quality prints.
The M9 offers excellent tonal reproduction (at least in the BW arena) over a range of six stops and a speed from ISO160 to ISO400, with just that visual occurrence of grain that is seen in most great photographs at high magnification. In addition to this there is high end definition with crisp detail as you expect from Leica lenses.
For me that is enough for the style of photographs the M series is designed for. I do not need HD-video options, Live View studio options and HDR options. As a photographic instrument the M has its limitations, as does every instrument, but what it does, it does with elegance and purity.
For the curious I have added a few photographs that show a picture as it is processed by the camera, an identical picture as seen by the software before interpolation (reading the image data from the file without corrections) and an enlargement where you can see the actual pixels.
Leica M digital intermezzo 2 (november 13, 2009)
Where is the smile of the Cheshire cat?
In the German magazine, der Spiegel (the Mirror), there is an interesting section about analog photography or Filmchemie-Fotografie. The aim is to create a bit of a revival of classical photography with film. You cannot make headways nowadays without contemporary measures and the project can be followed on Facebook and Flickr. Great classica cameras like Hasselblad and Zeiss lenses can be bought for a handful of dollars and even less Euros and film is still available, even if you have to buy it online. But who doesn’t do much of their buying on the internet now?
One of the arguments to use films, is the specific color representation and grain impression of AgX material. This feature is now grossly neglected in the striving-for-perfection-and-uniformity in the digital arena. I have the big Magnum book on my table on a bookstand and can easily leave through the pages. The most arresting images are frequently the ones with special colors or monochrome tonality.
I noted in my blog and in my recent review of the color reproduction of the M9 and M8 that I prefer the different representations of the current slide and color films over the uniform reproduction of the digital post processing. The ubiquitous use of software test tools bring to the fore the slightest discoloring form the established norm (the Macbeth or other cards). In the film days no one would strive to reproduce the Macbeth colors perfectly, but the card was used to note the differences and how to use these differences to get the required color-images.
In this respect we may note the bad influence of the magazine- and internet-tests. It is nowadays extremely easy to calculate the color deviation in DeltaE values and conclude that big differences can be equated with bad quality. This is of course not true. Chemists in color photography often purposely changed the color reproduction from the possible to the desirable. It is known for a long time and digital capture does not change this, that pleasing colors are not the same as accurate colors. Kodak had a special film in its range that was tuned to get real colors, but that film was not very popular!
It was easy and is still easy in AgX days to see the special qualities of Leica pictures. It may not be obvious anymore, but the famous Leica fingerprint for images was the mixture of lens characteristics and the interaction with silver-halogen crystals. It is becoming increasingly difficult to discern the special Leica quality in todays digital image capture. Over a period of five years I have intensely photographed with Olympus E-1, Canon 5D and Leica M8 (with and without IR filters). If I print comparable images made with any of these three cameras and put them side by side on a table and ask for differences, hardly anyone will note specific Leica quality or Leica fingerprint.
To be honest, it is still there, but it becomes increasingly difficult to separate the image world in Leica versus the rest. It is not yet impossible, but the current tendency for uniformity in imagery, inspired by indiscriminately using the same test tools and demanding that results should be as close as possible to a norm, may be the cause for the Leica fingerprint to become an endangered species.
Perhaps the Leica digital designers could reflect on the peculiar characteristics of the Leica imaging chain and dare to offer a color space and a post processing algorithm that is not as close as possible to the norm, but supports the Leica fingerprint in image reproduction. And maybe Leica users should support the fact that Leica images are and need to be different from the mainstream norm.
In lens design the Leica solution has never been the easy way to design a lens that conforms to popular criteria, but to create a lens that supports a special vision of the world around us. Zeiss used the same approach but had a different view and that is fine because we had the choice. Now the relentless competition and universal support for uniform perfection is killing that precious characteristic. When you see the qualities of the Leica lenses as exposed by the famous K8 MTF equipment, you cannot but admire the design choices. After processing the digital image files, these characteristics start to fade.
In AgX photography is is easier to detect the Leica fingerprint. That is why the M7 and MP and the range of M6 versions are still in use and will stay in use.
My view is this: testing is more than just listing a range of numerical values, produced my software or physical instruments. Without knowing what these figures refer to and the context in which they are produced and the relevance of the numbers it does not make sense to compare results. And you should, when necessary, dare to say that deviating results are not always to be avoided, and should be supported when it helps to get interesting and important photography. I received many emails from readers who noted that my focus on the core of the photographic art and science is indeed a welcome approach that helps to create a proper distance from the tendency to use numbers as the defining norm for photographic quality.
Now the task is to rediscover and define the Leica quality in the digital realm.
Leica M9, part 7, colour reproduction and noise revisited ( 2009)
In the days of silver halogen emulsions, grain, sharpness/resolution and tonal range were characteristics of the image that were intensely studied and measured. It was found that when grain became smaller, the sharpness impression decreased, the resolution increased and the tonal range decreased. Several other fixed relationships were established, like sharpness impression increased as grain increased and speed increased. Many photographers were disappointed to discover that finer grain did not bring greater visual impact.
Discussing graininess is quite difficult. A real comparison is only possible when lab conditions are strictly observed. One needs the identical density and the identical CI value (steepness of gradation curve) to make meaningful comparisons. If you compare films then preferably the same developer should be used. When comparing developers, the same film and same densities are required. This was seldom the case and all kinds of wild assertions were common. For decades the debate ranged between supporters that a specific film and developer combo would present best results. And claims about resolution ranged widely for let us say a Tmax 100 film between 50 lp/mm and 200 lp/mm. Notorious is the claim that a certain lens/film combo could resolve more than 400 lp/mm or the claim by the Gigabit manufacturer that this film could resolve around 500+ lp/mm.
The basic issue here is the fact that there are no reliable standards and definitions and that the number of parameters is so high that every claim can be made and even supported.
We have now unfortunately the same situation in the digital realm. In fact the situation is even worse. It is very easy to do a noise or resolution (lp/ph) or colour analysis: many programs are available and anyone can design his/her own analysis program. Understandably every result will be different. Not necessarily wrong. But it is impossible to directly compare results because of the greatly differing conditions. The only option here is a rational discourse, not a lawsuit. Comparing results and comparing methods is the best way to analyse and explain the differences. But camera users are quite often not interested in independent lab results, but in numerical values, however achieved at, that support their convictions and expectations. If you want to believe that the noise behaviour of the Leica M9 is better than that of the M8, you will not be inclined to read with interest and an open mind the results of a report that concludes otherwise.
This state of affairs has resulted in the establishment of international standards, most prominent the ISO standards. The ISO norms for, as example, noise and resolution define the procedures and test conditions that need to be used to analyze the topic defined.
Signal and noise are the prime characteristics for categorizing imaging performance. Signal is defined as any response that provides valued information and noise is defined as any response that detracts from a desired signal. A signal can be measured by two broad metrics: OECF (opto-electronic Conversion Factor) and SFR (Spatial Frequency Response). Noise can be measured by NPS (noise power spectrum) and spatial distortion, like aliasing.
For any metric there is a range of secondary measurements that define part of the metric. As example: OECF considers sensitivity, tone, exposure, white balance. SFR is related to MTF, but not the same.
A main characteristic of OECF is the fact that it is based on larger areas of the image (the region of interest). Noise analysis is often based on small areas of the image. Signal to noise ratio (SNR) combines both metrics, but there is a difference when calculating the SNR using large or small areas of interest.
In my test reports I use the programs that support the ISO standards, like Imatest, Image Engineering and Image Science Associates. Many of these programs rely on Matlab routines to do the job. Matlab itself has a wide range of image tools with which one can analyse and calculate almost everything in the digital imaging realm.
The results of the OECF measurement procedure are consistent with practical experience. The combination of dynamic range and SNR gives information about contrast (or signal) and the probability of detecting that signal, which is noise. You can measure signal as a separate density patch or as an incremental signal, like the classical Kodak step wedge. In the first case you use a noise-cracking technique that separates rms noise from random temporal rms noise. In the photographic practice the just noticeable density differences are often more important than the grain pattern itself. The calculation of the incremental signal/noise is the derivative of the OECF function.
I have expanded a bit on the theory behind the several types of measurements to warn against the indiscriminate adoption of results without insight into the way the results are arrived at.
Several image quality studies have found that SNR values of 40 and 10 represent excellent and acceptable levels of image quality. These levels are the basic for the OECF definition of good (that is useable) dynamic range.
The most important topic is not the fact that one can deliver numerical values, but the question how these numbers can be related to practical photographic topics. Just as grain is not always objectionable, so is noise. And the quest for the highest resolution is sometimes other-worldly. And there is always the topic that the screen does not represent the image as it is printed on paper.
It makes sense to re-examine the procedures when the results are being questioned. I photographed the Macbeth chart again with the M8 and M9, both fitted with the same lens. To keep the flow of data to a practical level I restricted myself to the ISO2500 setting. The chart was photographed with several WB settings, appropriate to the ambient lighting, in this case Auto, daylight and cloudy. The exposure was set according to the reading with the Gossen Mastersix and a range of exposures was made with half-stop increments over a range of +/- three stops. Both cameras gave an over exposure of one stop when the in-camera exposure meter (on Auto) was used, compared to the official grey-card reading.
This analysis points to several conclusions. The noise pattern is not consistent when using different over- and under exposure values. The pattern does change when using different colour calibrations (daylight, cloudy, flash) and the pattern does change when using different raw converters. None of these conclusions should come as a surprise. Leica users, still versed in AgX technique will recognize these trends as what you expect in grain patterns when using different exposures and chemical developers.
I checked the whole bunch of image files to find the optimum for the M9 and the M8 camera and then did the noise analysis on the bottom row of the Macbeth card. The results you see below, for the JPG version and the Raw/TIF version. There is only a slight difference between the two cameras and the M9 is a fraction better in the noise reduction. Note too that by optimizing the colour response, the blue cast of the M9 images is gone. Red the colour paragraphs for more information on this topic.
These are the optimum pictures. It became evident under the inspection of the large amount of pictures (I made more than a hundred pictures with every camera: grey cards with exposure bracketing and the full range of Kelvin values from 2000K to 12800K and the Macbeth card with the same options) that the M8 is a much more sensitive instrument than the M9 as far as optimum results are concerned. It is much easier with the M8 to take sub-optimum results than with the M9 which has a more stable result pattern. From this perspective the M9 is more user friendly camera that the M8. Even when you wander away from the optimum, the M9 brings excellent results. The M8 on the other hand brings much lower results when you do not operate at optimum parameters. This phenomenon may explain the fact that many M8/M9 comparisons favour the M9 results. The M8 can bring results as good as the M9 but needs to be operated within narrow limits. But if you care to move on from the role of Leica aficionado to Leica expert the M8 is a most pleasant and potent camera to use.
The overall conclusion that under many diverging situations and conditions the M9 delivers the more consistent quality is true too. The M8 operates in a more narrow band when optimum results are required and when these conditions do not apply the result is not as good as that what you get with the M9, at least at higher ISO values.
The calibration of the colour response of the M8 and M9 do differ: when you study the Exif data, you will discover that the colour matrix has different values for both types of camera model. A direct comparison between the colour behaviour of the M8 and M9 is not advisable.
As example:Macbeth card, daylight illumination: the M9 on Auto sets the white balance to 4870K, Daylight to 4351K, Cloudy to 4996K. The M8 on Auto sets the white balance to 5509K, on daylight to 5083K and Cloudy to 5922K.
These values also change when using different ISO settings and when there is under- and overexposure. In itself this is not a problem. Experienced users will select the colour response according to taste and intended use. When selecting colour slide films you have the same problem. It is usual for critical work to use filters and to fine tune the colour reproduction. The recorded values were analysed using the new version 5 of Capture One. It will be no surprise to learn that other programs will give different values: as example the same picture in Capture One 5.0 gives 5102K, where PWP gives 8870K.
The colour calibration does also influence the noise pattern, especially in the darker parts of the scene.
Generally when using the RAW setting of the camera, the RAW program operates on the luminance values of the pixels and the Bayer pattern to construct the colour for every pixel. In most commercial programs these algorithms are proprietary and highly efficient. You cannot influence the algorithm, but you can sometimes choose between different ICC profiles. Several of the smaller RAW programs let you create your own camera profile. In all cases there are two profiles you have to consider: the input profile (the camera profile) and the output profile (like sRGB, Adobe RGB or wide gamut RGB). These choices have their effects on the final colour representation of the image. And none is perfect!
I used the Macbeth card and Capture One 5 version and the generic profiles for M8 and M9 to generate the image files. In this case I let the program decide what colour space to use and selected the Auto option. This file was then exported in the three colour spaces mentioned (sRGB, aRGB and wgRGB) and analysed with Imatest. The six results are shown below. Note that the differences overall are quite substantial and that within a colour space some patches are better or worse. It is very demanding to make general and sensible conclusions. One of the options is to do some calculations and find the average deltaE variations. This is a common practice, but I cannot recommend this one, as the deltaE variations assume a linear correspondence between numerical values and visual impressions which is not the case. The eye is much more sensitive to small variations in one colour than in another.
The second approach I used is an option within the PWP program. The Macbeth card has accurate values for every patch and these values are published. A program can read the photographed card and compare the values found with the internal accurate values and map accurate values on the photographed values. As values differ for every patch the program does a best guess to find the best overall match between recorded and accurate values. This I did for the M8 and M9 image and exported the results to the three colour spaces and analyzed the results with Imatest. Below are the results: they differ from the ones above, I would hesitate to add
The Macbeth card is a simple test as it only has 18 different colour patches and six monochrome ones. But even this limited range of colours is never fully accurately captured or calculated in post processing software.
But colour psychology insists that accurate reproduction of colour is not always the best option: if it were, the Kodachrome films would be still widely used. Here I can give only one advice: the advantage of digital capture and recording is the ease of use and the cheapness of the process. Experimenting with the several options (input profiles and export profiles and not to be overlooked printer profiles) for the type of pictures you like to make and see is the best approach. With film you are stuck with a limited colour bandwidth and a small possible overall change by employing filters. In the digital realm, there is a wider gamut of options. More like what painters have. Colour is primarily a psychological phenomenon relating to emotion and mood, not a colorimetric exercise. The Leica M8 and M9 do differ in this respect, but with careful calibration of the input and output parameters one can get the colours one likes and it is even possible to have the colour reproduction of both cameras to converge to a large extent. To claim that one camera is much better than the other is a dangerous game and an unnecessary exercise. And this goes too for the comparison between the Leica M9 and other non-Leica models, like the Canon or Nikon cameras. In straight recording Nikon and Canon have an advantage as their colour profiles are optimized for skin reproduction and other often selected colours. A point to consider is the fact that colour shifts in the M9 and M8 space have a more pronounced effect on the other colours where the high-end Nikon and Canon cameras have a more balanced behaviour.
To recap: colour reproduction is a science and a complicated one. It is very difficult, at least in my opinion, to make general statements about the colour quality of a specific camera. A reviewer can present as much factual evidence as one can handle, but subjective conclusions should be used very sparingly.
Where do we stand at this moment?
The Leica M9 is a most delightful camera to use and even own. It does not convey that peculiar proud of ownership one feels when handling a film loading M model, but as a photographic tool it delivers sound performance.
The characteristics of the M9 bring it close to the dslr competition without however blasting to the top. In this sense the M9 is the true successor of the M5, because that camera too left behind a few precious M features to add aspects that update the camera to the modern times.
It is still too early to label the M9 as one of the very best or one of the great or one of the many excellent ones on the market.
The current tendency to profile the M8 as a flawed toy and to profile the M9 as one of the best digital cameras in the world is a bit myopic and disregards the many qualities of the M8 as a photographic tool. The IR bias can be put to good use when doing black and white photography in the wider sense of the word. The M8 is a more demanding camera than the M9 is and to get excellent results with the M8 asks for some additional determination. But even the M9 is not a fully mature product and needs some expertise to take great pictures.
In the next part we will conclude this essay and offer some perspective on the role and position of the digital CRF in the current imaging world.
Colorimetry and the Leica M9
The human visual system is an extremely efficient system for color perception, but also very flexible and easily fooled. Any color can be characterized by three color quantities: brightness, hue and saturation. The physical nature of color is based on the fact that different wavelengths display different hues. The colors we see depend on the spectral composition of the illuminant and the nature of the object (what wavelengths are being absorbed and what is being reflected) and the physiological and psychological make-up of the viewer. This combination accounts for the widely diverging opinions on color appreciation and evaluation of a certain scene. Two observers of the same picture (nowadays almost invariably on a computer screen) may see different skin colors of the same face and one may conclude that the reproduction of the skin is wrong. This conclusion is a psychological one and depends on a wide range of variables, the specific illuminant being only one of these. Even the fatigue of the viewer, the color memory of the viewer, the specific spectral sensitivity of the viewer’s retina, the spectral balance of the computer system and so on have influence on the color perception.
Given this wide variety of conditions, it is logical that color scientists have established standards for every component in the reproduction chain. It would be easy to relate the wavelength frequency to the color sensation, but that is not the case. The ICI (or CIE) commission has first defined a standard observer with fixed primary colors (blue, green and red with wavelengths of 435.8, 546.1, 700 mu) and fixed intensity in lumens. Secondly there have to be standard illuminants with well described spectral composition. The CIE has defined three standards: A, B and C representing tungsten filament, sunlight and overcast sky.
The standard illuminants are derived from a black body radiator where the spectral power distribution is known and can be expressed as a color temperature in kelvins.
It is an established fact that three well-chosen primary colors can generate any other color. Two popular systems are the additive system (RGB), used in solid state imagery and the subtractive system (magenta, cyan, yellow) used in silver halide color photography.
It is simple to create a triangle with red, green and blue as its corner points. On the green-red line we find all mixtures of red and green from yellow-green to orange, on the red-blue line we find all shades of purple and on the green-blue line there are all blue-green hues. This triangle is called the RGB Chromaticity Diagram.
In the silver halide technology the situation is quite simple: we know the illuminants, we know the chromaticity diagram and the chemical behavior of the color dyes in the emulsion layers. With this information we can create films with the required color representation. We have two options here: accurate and pleasing representation with most manufacturers going for the second option.
If the light source is not one of the standard sources, which is most often the case, we can use CC filters to change the color temperature. Using a color temperature meter, we can find exactly the difference in kelvins and select the appropriate filter (in fact the meter will tell us what CC filter to use). The u-v diagram shows the chromaticity of the full radiators as a black line. The u-v diagram is constructed such that the distance from a color to the black line can be used to estimate (calculate) the required correction.
The need to work with exact numerical values came when color television was introduced. A color television system has color filters and light sources used at the transmitter and receiver component and they must match over the whole chain. So numerical specifications of a color that define hue and saturation (brightness is not defined as it simplifies the calculations) are required. These specifications are based on the chromaticity diagram and the standard observer.
The spectral points that have been chosen implies that not all spectral colors can be represented. See shaded part in picture below. The triangle is a two dimensional construct and every point can be found and calculated with simple algebra and when necessary with matrix operations.
Given the coordinates and the reference points one can define a new set of coordinate axes and transform from one system to another. The RGB diagram cannot handle all colors and a new one has been defined, the XYZ chromaticity diagram. This one can represent all spectral colors but has one disadvantage. The colors are described as a pair of numbers, say 0.3 and 0.7. There is no clue what wavelength is represented (in this case 550 mu). Therefore yet another system is used, one based on dominant wavelength, purity and luminosity. The advantage of this system is that it can be transformed into two signals namely chroma and luminance and this is the basis of color processing in digital cameras.
It is in fact amazing how much television and video technology is implanted in the digital photography processes and techniques.
Color information must be coded and normalized if we want to ensure that we get the colors we want. Basically we choose the primary colors (coordinates in the XY system), the white point (more difficult: the white point in the diagram is called white C, but for the recording system we use white C with maximum luminance (if the luminance is less than maximum we have a grey shade)) and finally we need to normalize the luminance signal. The assumption for this approach is the linearity of the transmittance system. This is not the case and we need yet another correction in the system: the gamma correction which has its influence on saturation and sharpness.
The above description is valid for television systems, but needs some additional information to apply to digital camera systems.
The M9 uses a CCD sensor with a Bayer pattern color filter array (CFA). The single pixels record only a luminance value for the particular color in the CFA pattern and a full color image requires a method of color interpolation.
Stage 1:The raw output from the sensor is a mosaic of red, green and blue pixels with different luminosity/intensity. An RGB image requires that every pixel has numeric values for red, green and blue for exact location of the color with the coordinates in the chromaticity diagram.
Stage 2: Interpolation: The camera employs specialized demosaicing algorithms to calculate the missing values for every pixel. The basic idea is to use a 2 x 2 array as one full color spot. This works fine, but has a major drawback: the resolution in horizontal and vertical direction is halved! One could use overlapping 2x2 arrays to extract more image information. The amount of algorithms is quite large and every one has its own balance of qualities. But the algorithm can be tricked: fine image detail near the resolution limit can produce moiré artifacts in several patterns depending on the original texture and the software used to develop the raw image.
Below: a comparison between the scene and the Bayer representation
Stage 3: AWB: the color values after interpolation must be adjusted such that they reproduce natural looking images that please the human visual system. The image will be adjusted as if it were taken under a canonical (reference) illumination, often daylight. The automatic white balance does this. But the AWB performance and efficiency depends on the quality of the demosaicing algorithm (DA). Both are mutually dependent. The final resulting image will be different if we first do AWB and then DA or the other way around. The AWB values are adjustments of the blue and red channels in the image (green is always set to 1). These parameters are referred to as gain. Changing the gain of the red and blue channels changes the White balance.
Stage 4: Color rendering: the color signal values processed in the previous stages must be mapped on a defined color space to create physical meaning. This color space (Farbraum in German) is crucial for the understanding of the color management. The color space is constructed as a 3 x 3 matrix where the numerical values are arbitrarily chosen. There are two options: scene-referred image data and output-referred image data, the first tries to reproduce the original colors (tristimulus values) of the scene, the second tries to produce user-preferred colors. Most cameras, including the M9 use the second approach: the color space is typical for the Leica M9 and designed by the engineers such that the sensor and filter characteristics and the idea what a good color picture should be. The usual color test to find color value differences between a test target (Macbeth chart) and the digital image have only limited value as the color spaces often have dedicated changes in the color reproduction.
An additional complication is the exposure setting of the camera. Exposure for optimum raw processing is too dark for normal processing.
Stage 5: the pre-processed raw data are stored in a file that can be read by a Raw developer program. A simple but very effective one is Dcraw, but more common ones are Lightroom and Aperture and so on. Leica stores the data in the DNG format.
Below you see a portion of the EXIF data as stored in the DNG file.
Color Matrix 1: 0.856 -0.2034 -0.0066 -0.424 1.36 0.292 -0.074 0.247 0.898
Color Matrix 2: 0.626 -0.1019 -0.047 -0.373 1.145 0.193 -0.1409 0.295 0.621
Camera Calibration 1: 1 0 0 0 1 0 0 0 1
Camera Calibration 2: 1 0 0 0 1 0 0 0 1
As Shot Neutral: 0.4599663111 1 0.7648926237
Baseline Exposure: -0.5
The tag “AsShotNeutral” has the gain values for the red and blue components
Above you see the values for the Automatic setting in the M9. Below you see the values for a chosen Kelvin setting
As Shot Neutral: 0.4614301405 1 0.7568366593
The values of the color matrix and the as-shot-neutral tags are used by the RAW programs to calculate the final colors. Every program has its own interpretation and calculation and results will differ.
I made a simple test with a Kodak Grey Card and a Sekonic Color meter. The meter gave for the ambient light a value of 5950 K. I set the camera to the full range of options for white balance, including the K values.
Below you find a table of white balance settings of the camera in kelvins and the results as calculated by some popular programs. Note that RAW Developer, based on DCraw produced the most accurate results.
With every program it is possible to change the Kelvin values and therefore the white balance. We know now that the K values are not registered in the EXIF file and that the internal processes of the camera change the gain values when you select different white balance options.
The basic question now is what sense does it make to change the white balance settings when you take the pictures, as the camera records the gain values and the RAW programs do their own (not known) interpretations.
For this moment we can conclude that the camera settings give approximate values and do their own interpretations of the internal color space and gain settings.
More in the next article.
Leica M 9, 35mm digital versus35mm AgX
Peter Drucker, the guru of management thinkers, noted that management is not a progressive science because the management problems of today are the same as of yesteryear. The same dilemma’s and the same choices keep popping up. This stationary status is being clouded by the enormous amount of management theories and fads and even hypes. In fact the same problems are being addressed by different and often wrong methods and approaches.
Photography is in the same state: here too we find a very stationary situation: most of the major photographic themes were fixed already in the period 1880 to 1900, when landscapes, portraits, reportage, nudes and war pictures were defined as artistic categories. And the big photographic challenges are still the same: correct exposure, interesting angle of view, proper use of light, proper fixture of the moment. This handful of everlasting problems is being covered by an immense amount of cameras, cameratypes, technical expertise and equipment functionalities. Film-loading cameras and AgX technology use basic thinking to get to the bottom of the problem. Digital capture and digital image files have brought new technology and will create unpredictable consequences.
One of the most overrated topics at this moment in the digital arena is the issue of noise. It is easy to see and somewhat less easier to measure in a predictable way, but it is only a problem because digital sensors can be tweaked to very high signal-to-noise ratios. ISO values of 5000 and more may sound impressive and because one camera has it, all want it. But I do not see what of the basic photographic problems is being solved by shooting at ISO 5000. In AgX technology the useful speed was limited to ISO 400 and some used ISO 1200, but that was already an extreme situation. If you limit the ISO values on the digital cameras to 400 or 800 there is no noise to speak of and you can get fine pictures in most situations.
For the comparison between film and sensor with the same size I used the M9 at ISO160 and the M7 with Ilford Delta100 at ISO80 and Spur HRX-3 and also Spur Orthopan UR with Nanospeed UR at ISO20.
The ISO20 may be dismissed as ridiculously slow when compared to the speeds of 12000 and more that are being promoted as must-have functionality, but on a cloudy November day I could take handheld pictures with the M7 and the Summilux-M 1.4/50mm asph. wide open at shutter speeds of 1/125 to 1/500. Good enough for me and delivering very pleasant out-of focus scenes with clearly defined sharpness planes.
For the comparison test I used testcharts and a tripod and as lens I selected the Elmar-M 3.8/24mm asph. When the aperture is set to f/5.6 the resolving power of the lens exceeds the 100 lp/mm boundary with ease and with high contrast. On the MTF equipment the contrast value of 50% was found at 80 lp/mm. The performance of this lens does not limit the capabilities of the cameras. To eliminate focus errors I used the magnifier 1.4 and set the distance at 1.2 meter. At this distance you can visually detect any focus error.
The Leica M9 could resolve with good clarity about 60 lp/mm. This is close to the Nyquist limit of theoretical 73 lp/mm. These values are the same for the M8 as the pixel pitch is identical. The effect of the thicker filter on resolution is hardly detectible. I have remarked in previous reports that effective resolution is about 15% lower than the Nyquist limit. This is borne out in this case with the 60 lp/mm on the image file.
The Ilford Delta 100 is in speed comparable with the basic speed of the M9 and is therefore a good comparison. This film in Spur HRX-3 (very fine grain, good sharpness) delivered a excellent 70 lp/mm and with some reservations a useable 80 lp/mm. For most intents and purposes we can say that the M9 technology in 135 sensor size supports a performance that is now as good as that of one of the best medium speed films with the same size and identical settings (magnification and lens).
The Spur Orthopan UR is derived from the Agfa/Gevaert Copex HDP13 and identical to Adox CMS20. These references indicate outstandingly fine grain, but a restricted tonal range. But the Zone System has 6 stops useful rage and this film is above 5 stops. But is a resolution champion and here we see that digital has some distance to travel. The Orthopan resolved 125 lp/m with excellent definition and clarity and had a useful 140 lp/mm. The limit was found at 160 lp/mm but that value is not reproducible on paper. This film in the M7 then has twice the resolution of the M9. For handheld photography the differences are smaller of course, but when you want or need to exploit the limits of the optical/mechanical equipment the very low speed film is the only choice and there is no fear of noise. Even the S2 will be defeated by this film/lens combo. It is true that the deployment space is limited: tripod, careful technique, good lens, low tolerance equipment, but these are the prime characteristics of the Leica camera.
Digital technology is the first choice when speed, ease of use, and the need for hundreds pictures in one shooting session are in demand. I can see a pairing of digital and analog, especially in the case of the Leica CRF with the M9 as the main camera for large shooting volumes, ease of handling and processing and the M7/MP (or any of the other M cameras from M3 to M6) for careful work where finest details at large print sizes and the look of classical pictures is required. The sometimes harsh sharpness of the digital processing technique can be countered with the subtle and cultivated look of a fine balanced black and white baryta print.
In the B part of this article I will present the results of both technologies when negatives are printed on paper and the image files are printed with the Epson 3800.