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Mechanische camera's
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Mechanische camera's

Leica M7: One step closer to perfection

The introduction of a new Leica camera is always preceded by a longer period of gossip and speculations. The mythical electronic Leica is a subject of discussion since 1996 and many expected the new M camera at Photokina 2000. “Insiders" predicted that the new M7 would be the Konica Hexar RF with a red dot. To shed official light on this topic: The Konica people have proposed to Leica to market the Hexar as a joint effort. But Leica refused as they assumed that the Hexar did not fit into the Leica philosophy of photography. Others “knew” about the R&D activities, investigating a faster version of the shutter with a higher synch-speed. But wishful thinking should be separated from the normal lab research. From the original Leicaflex on, research into improved shutter designs are part of the culture of the engineers, as is research into all kinds of improvements and new products. Now in spring 2002 the M7 is real. The camera does not fulfill all characteristics that were part of the wishlist, except for the aperture priority automatic exposure. I am happy that Leica did not listen to all suggestions and followed their own ideas and philosophy.

Product changes: careful evolution. 
 A new Leica model with radically different functionality is relatively scarce. The M3 from 1954 was a very different camera from its predecessors, the IIIf (1950) being the comparison. The M2 and M4 offer hardly any substantial improvements and we have to wait for 1971 with the M5 to witness Leica making a big effort to jump out of the self imposed limits. That is 17 years after the M3! The M5 did not become the success the Leitz people had hoped for. The automatic exposure metering with manual selection of either shutter speed or aperture was very accurate and the semi-spot metering with the 8mm sensor was quite nice and functional.  The size and shape of the body  gave the camera a somewhat chunky look. Leitz assumed that the users of the M5 would be mostly interested in the enhanced functionality, as the innovative two  lug carrying strap indicated. The classical engineering rule that form follows function was put into practice. The failure of this camera to innovate the rangefinder scene still resounds in the halls of Solms.
The next models, M4-2, M4P and even M6 did not add much to the progress of the rangefinder camera. The M6 offered the same functionality as the M5 did, but with a different implementation. And incorporated into the same now classical body contours. From a broader perspective, the M6 did not improve substantially on the M5. The M6TTL is the first model to add new features and it is significant that the body size had to be increased by a height of 2mm to incorporate the new functions. The M7 from 2002 is again a substantial change in the line as was the M3 in 1954 and the M5 in 1971. But now we are 31 years later since the introduction of the M5.
M3, M5 and M7: three models in a 48 year period.         
The M3 is composed of about 860 parts, counting every screw and washer. The M7 has 1300 parts, and again every electronic component has been counted as a separate part. 350 of these parts are new and/or improved parts when comparing to the M6TTL. Two hundred of those parts are electronic and 150 are mechanical.
The manufacture: tradition and modernity meet.
I happened to be in the Portugal factory when the first new M7’s started to be manufactured. This camera is an astonishingly clever mix of old and new production technology. In the Portugal factory you will find the original equipment, made in 1953 by Leitz for the production of M3 parts. These machines have the classical green color of most mechanical drilling and milling machinery, all moving parts are thick with grease, and the smell of cooling liquid and oil is impregnating your clothes. Even the sewing machine that has been used for over 70 years to stick the silk threads on the shutter curtains, is working continuously, operated by extremely skilled hands of a young woman.
 The engineers know that these old machines cannot be improved upon as they have been designed with only one dedicated single purpose. Precision and functionality have been optimized as this equipment has been designed for the manufacture of one single part, and to do it with utmost accuracy. So there is a large amount of components in the M7 (and the M6TTL and M6) that are identical and identically manufactured to the M3 days.
 Intermingled with the dull green machines, you see modern bright red and white CNC machines. These Computer Numerically Controlled machines are very flexible and can be programmed to execute very complex movements and  intricate processes. Again the accuracy will be measured in less than one hundredth of a millimeter. Be careful here. It is relatively easy  for a skilled worker and the right equipment to manufacture individual parts to a thousandth of a millimeter. But only if every part is individually and manually finished on machines with even tighter tolerances. To transfer this level of accuracy to a process of series production is impossible.  In any larger scale production you are hard pressed to stay within 0,01mm all the time and within statistical error margins.
 The body of the M-camera has about 80 holes that need to be drilled into the diecast chassis. In the past any machine could only drill a few holes and then the body had to be refitted to another machine for the next series of holes.  This is error prone as the worker would not be able to fix the body at the exact position of the previous operation. Nowadays the CNC machine can accomplish all actions on one body without any refitting. The result is a higher precision of the location of the holes.  This same mix of tradition and modernity we meet in the M7.
The aperture priority automatic exposure.
 The electronic shutters, used in the Hexar RF and the G2, consist of a compact integrated unit that combines the vertically running metalblade shutter with an electrical  filmtransportmotor. To ensure that no unwanted light reaches the film, the shutter needs to be cocked immediately after the shutter-release. It might be possible to incorporate this mechanism into the current M-body size, but the interior of the camera has to be regrouped substantially. Most important however is the fact that the M would loose its very heart and soul: the silent, slow moving, vibration free horizontally running cloth shutter.
 Therefore the decision in Solms has been an 'easy' one: keep the current mechanism and govern the shutter speeds by electromagnets and a new chip.  Presumably the engineers had no idea how difficult this simple decision would be in the real world of engineering mechanics and electronics. The M7 was targeted for Photokina 2000, but marketing wishes have no precedence over sound engineering requirements.
 The mechanical version of the shutter (since M3 till M6TTL) is of the constant speed, variable slot-width type. The two shutter blinds run separately and the time interval is determined by the shutter speed dial setting. When we depress the button, the first blind is released and runs across the film gate. The second blind is held in position by a connecting pin, better described as a holding catch. The timing of the release of the second curtain is controlled by a very intricate collection of cams, levers and sears. The main roller that tensions the springs also holds the speed adjustment mechanism. This roller rotates over almost a full turn and this movement is used to allow a curved speed cam a certain time period to release the catch of the second curtain. The time to transverse the film gate varies from 18-22 milliseconds. The target speed is 20.8 milliseconds. That translates into 1/48 sec. and this is with some safeguarding the 1/50 sec for the flash synchronisation. The speed of the shutter curtains then is 2 meter/second or 7.2 km/hour. This speed must be forced to zero and compares to the force as if you with your bike would crash into a wall. That is some force and that is why Leica employs two brakes, each for every curtain. The dilemma is clear: higher speeds means more braking force and more noise and more tear and wear. But there is even more to consider: the complete assembly of the shutter mechanism with all its springs, levers, gears, wheels, shafts and spindles has over forty different points (areas) of friction that together regulate the accuracy and regularity and speed of the curtain movement. The higher the speed, the more difficult it becomes to guarantee the evenness of travel. Tests made by the factory indicated that 1/2000 might be possible but not within the required very tight tolerances for accuracy and evenness of travel and the demand for low noise and absence of vibration. The Leicaflex has also a mechanical shutter and can handle 1/2000. The explanation is a different shutter mechanism with several small shutter drums where the M shutter has one big one.

To expand a bit on this topic:
The slit width of the M is 36mm when the shutter speed is 1/50 and the speed of the curtains is about 20 milliseconds at all times. A calculation shows that for he 1/1000 the slit width has to be 36mm divided by 1000/50 (the speeds). This is 1.8mm. In reality the slit width is a bit wider (at 2 millimeter). Now for the 1/2000 the slit width would have to be about 1mm. That is very small and it is hardly possible, given the geometry of the shutter to crete a relaible and constant slit width of 1mm. You should remember that the Leica shutter is a bit more complicated. When the shutter starts it is not at full speed from the very moment. Like every mass, it has to be accelerated by the tension of the springs and so it starts slowly and accelerates to full speed at the end of the travel, where the braking action is. Without compensation, the film would be overexposed at the beginning of the travel (shutter starts to accelerate) and underexpose at the end (shutter races full speed to its stop). The mechanism compensates and therefore the slit width at the beginning is smaller and later wider than the nominal 2mm. For the 1/2000 the same principle holds, only with too small toerances ato be viable.
The only option then is to increase the speed of the curtain travel, like in the Leicaflex. This shutter is a complete different design. You will have to wait for my new book for a detailed explanation. Suffice it here to say that the braking force is too high for the M-shutter mechanism. The M7 has the same topspeed as most Leica RF models since 1935.
We should not overvalue the need for faster shutterspeeds. While there certainly is sometimes the need for speeds faster than 1/1000, we should note that with ISO100 film and a blazing sun, we need 1/1000 and f/5.6 for a correct exposure. That will do for most situations and subjects. If you wish to use a narrow depth of field that you can get when using f/2.8 or f/2.0, even 1/4000 will not be of much help. 1/1000 @ 5.6 is of course identical to 1/4000 @ 2.8, but for narrowest DoF you may need f/2 and then 1/8000 would be required.
Electromagnets and an additional ball bearing!
The electronically governed shutter in the M7 is thus identical to the one in the M6 (or M3). Same design, same mechanical components. The speed adjustment mechanism with the gears, cams and levers has been replaced by an electromagnet, one for every curtain, that regulates the timing of the release of the curtain. What is lacking is the geartrain and the noise of the gears that retard the second curtain during the slow speeds. Where you can hear the soft purring sound of smoothly engaging cogs when using the slow speeds on an M6TTL, with the M7 you do hear  silence. Just twice a soft clicking sound of the braking action of both curtains, the second one being a bit louder. At higher speeds, the sound is very close in character between the electronical and mechanical versions.

The electronics make the shutter battery dependent. The drain on the batteries (now  make the shutter battery dependent. The drain on the batteries (now two batteries in the compartment) is very modest, but is still advisable to have a reserve pair in your bag. The fear that the batteries and electronics do not cope with severe climatic conditions is not supported: even in extreme cold the M7 shutter operates without any failure and is even more accurate than the mechanical one. The speed dial can be moved with one finger and speeds can be set from 4 seconds to 1/1000 and B in every direction. All speeds are electronically governed, with the exception of the 1/60 and the 125 that are mechanical. The choice for these speeds is logical: these speeds can be used handheld with confidence and are slow enough for many lower light situations, indoors and outdoors.
 This is how it works: In AUTO mode all speeds from 32 seconds to 1/1000), including the 1/60 and 1/125 are governed electronically and half steps can be selected. In manual mode (with batteries), the 1/60 and 1/125 are governed mechanically, all other speeds are governed electronically. All speeds can be selected from 4 seconds to 1/1000. No halfsteps can be selected. In batteryless mode only the two mechanical speeds 1/60 and 1/125 can be used.
Sometimes you can read the statement that in the mechanical M-models (from M3 to M6TTL) the shutter can be set at intermediate postions and give accurate speed settings. This is not true. You can set intermediate positions between the official speeds, but the accuracy of the shutter is not guaranteed. In fact it is quite unreliable and cannot be recommended. In the manual method, the finder shows the familiar diodes and symbols of the M6TTL exposure metering.
 In the AUTO position the speeds are set stepless by the exposure meter to accurately match the measured lightlevel. Full speed and half speeds are indicated in the finder (in the center of the lower part of the finder where the TTL diodes reside).  The selected speeds are stepless, but one should not take that to literally. It is not the case that every possible speed setting (1/33, 1/32, 1/31) can be selected, but rather there is a range of very small steps built into the chip. So 1/30, 1/35 and 1/40 may be possible but not the times within these: 1/31 will be set as 1/30. This level of accuracy will satisfy even the most critical user and film emulsion.  

Calibration of the shutter is done thus: The highest speed (1/1000) is adjusted, regulated and fixed by the mechanic during assembly. All other speeds are automatically correct as they are governed by the small steps as set in the Eprom. This level of accuracy needed the one big change in the shutter: the main roller now is supported by a rollerbearing. From M3 till M6TTL the bearing was a plain bearing. The new geometry of forces necessitates this change.
The measurement of the shutter speeds. 
It makes no sense to measure speeds when the camera  has just left the factory. You then get an idea of the quality control. What is important is the accuracy and longevity  of the shutter under stress. And as important as the speed itself is the constancy of the speed of the traversing slit. I measured two heavily used cameras. My own M6 (one full year of use since last adjustment) and an M7 (same use). Both had excellent constancy of travel.
 The results are in the table below:
First column: nominal speeds; Second column: M6; third column; M7. + means slower, - means faster

+ 5
1 sec
2 sec
4 sec

 The results for the M7 are very very good, but the M6 is certainly not much behind. Differences of 5% to 10% are irrelevant, even in scientific picturetaking conditions and even 30% (for the highest speed) is within the tolerance of even the most critical slide film. But such a difference might be just visible. For very critical black and white photography the results are very satisfactory. The M7 shutter has as advantages the lower noise, dead-on accuracy and the facility of automatic exposure control. The dependence on batteries may be for some photographers a culture shock. The mechanical shutter of the M6TTL delivers outstanding performance, that is now after decades of tuning and honing at its peak.
The practise of working with the automatic exposure control.
In the manual position the M7 is identical in operation to the M6TTL version. But remember that the times are electronically controlled. The essential change occurs when you select AUTO on the dial.  Picture taking becomes more spontaneous and even more relaxed. Once not being detracted by the need to adjust or even set correct exposure.  You start to photograph on intuition and emotional response with the subject. Now  you can concentrate fully on selection and framing of subject and give all attention to focusing. The primary choice of aperture is essential, as this regulates depth of field, selective focus and image quality. The choice of speed is a derivative act and as this is taken away from you by the electronics, you are relieved from that ‘burden’. During my use of the M7 I noted that many pictures were focused more precisely and accurately. And in border situations the exposure was improved too!  Specifically in situations with constantly changing light levels (street scenes with sun and clouds, shows, circus scenes) and scenes with severe lighting contrasts (dark spots one moment, contre-jour the next moment), where the quick selection of  subjects in differing conditions is needed, the AE is a gift from heaven (actuallly from Sol
I am convinced that this topic touches the heart of the matter: with the M7 you can fully concentrate on the subject and only select the  focusplane. This is a very relaxed  way of picture taking, still being in control of all important decisions and trusting the electronics where appropriate. The M7 should be close to Barnack’s vision: spontaneous and carefree photography with a sensitive eye and emotional involvement. The photographer controls the important aspects and makes the decision. The camera follows and supports.  The M7 is a true Leica: the clear and large finder, fast and accurate focusing, the smooth and direct action trigger and the civilized clicking of the shutter: all is there.
 Time lag.
Leica did a good job here: the response times of the electronics are very fast. The time parallax between pressure of the shutter release button and firing the shutter is 12 milliseconds (12 -18 ms with the M6). Compare this with the Konica Hexar RF (100 ms) and the typical single reflex camera (above 125 ms) and the current best digital cameras (400 to 1500 milliseconds) and you will understand that Leica designers know their job and are very dedicated to support the M-style of photography. The decisive moment is still the area of choice for the M7. The travel of the release button is identical to that of previous models. There is some tolerance here. Travel distance has a value between  1.9 to 2.1 mm.

So it might be possible to have an M7 with a slightly shorter stroke than an M6TTL. The M7 I used had a 0.1mm longer travel than the M6. But this is not structural, just within the tolerance band. The AE lock is very easy to use and convenient. The camera, in AUTO mode, measures the light continually. So if you move the camera over an area , you will see the speed indication in the finder changing all the time. Point or hold the camera to that part of the subject that is representative of the illumination you want to have metered, and lightly depress the release button. The meter stops measuring and you see a small point between the indicated speed digits. (With 1/1000, you see 1 ' 000; with speeds from 1/750 to 1/125, it is x ' xx and with the rest it is ' xx). Hold this, recompose and press the button. If you do it fast, you will see the AE indicator dot flashing for a moment.
The functioning of the exposure meter.
The M7 now has a on-off switch as a collar around the release button. No longer can and will you trigger  the shutter when the camera is put into or pulled out of the camerabag. Switch the camera on and for the first two seconds the warming up cycle starts and the selected ISO speed is shown in the finder.  After that period the camera measures continuously the light level. The camera is immediately ready for exposure when you fire the shutter with a preset aperture or after selecting an aperture before making the picture. These measurements take very little current. Again we see the care of the designers to provide the same speed of action and user support  as in previous models: The selected speed is indicated in the finder (where normally the diodes are displayed) with full and half speeds  (as example: 30, 24, 15). The numbers are red and consist of a group of 33 LED segments (as in your calculator) on an area of 0.7 by 2.3 mm. The enlargement in the finder is 15 times, and the brightness of the LED is variable according to the ambient light level. Fitting in this array in the confined space of the M finder is a major feat for the Leica engineers.
Exposure metering itself is not changed: it is still the familiar and proven method of measuring the light reflected from the whitish spot with a diameter of 12.1 mm on the shutter curtain. The corresponding area on the filmplane is always a circle with a radius of 6mm (image height). The measuring spot is often described as (semi) spotmeter. It is however best described as a center-weighted integral metering pattern. Results do indicate that the meter response is close to this time honored method and the M7 is even a bit more accurate.
New in the M7 is the automatic DX coding, and now you cannot forget to adjust the filmspeed dial when changing film. The dial now doubles as a manual filmspeed setting and an override from +/- 2 stops in steps of 0.3.  The great leap forward is the automatic exposure control in the M7. Not a big step in itself actually. Most cameras have this facility since many years.
The Leica user however wants to stay in the style and feel and results of the classical M-photography  and this often clashes  with automation services. The M7 is 100% pure Leica M with AE that fits seamlessly into the classical M-style. Take pictures with an M6 and then switch to Konica Hexar RF or Contax G2. You will have a long period of adjustment  and a steep learning curve to change your way of picture taking.  The switch from an M6 to the M7 is without any threshold.
 I used both cameras at the same time and could not notice any difference in style or approach. With one exception: the added freedom that the AE gives you by taking care of exposure, allows for such spontaneous, intuitive and intimate picture taking the M-photography  one step closer to perfection.
Slower speeds.
In B-position the time period is counted upwards (from 1 second to as high as you like) and indicated in the finder. This is very useful and now there is no need to look for some light to illuminate your watch dial. In automatic position the meter can set speeds till 32 seconds. These speeds are indicated in the finder too, but now counting downwards. The sensitivity is the same as with current TTL models (EV -2 at ISO100). The M5 had a sensitivity threshold of EV1.
Flash synchronization and TTL.
 In order to  use the TTL measurement, the shutter speed of the M7 must be set to 1/50.   With this speed the TTL functions correctly with dedicated flashguns (SCA-3501/3502) and SF20. With the new Metz 54 MZ3 a High Speed Synchronization can be used. The HSS function operates only with the combination MZ and M7 and now the faster  speeds from 1/250 to 1/1000 can be selected too.  The MZ3 works in manual mode only (not in Auto) and as the speeds of 1/60 and 1/125 are mechanically operated when using the speed dial (manual mode), the flash cannot be activated by these speeds. You can choose between synchronization on the first or second curtain. With the MZ 54 we can at last use fill-in flash on location with higher speeds and wider apertures.  For many this function will be of great value. Others will see it as unimportant as the M-domain is the available light photography. This however is too narrow a perspective. Luckily any photographer now has he choice to use the M as is required. The automatic TTL function is not supported with the 54MZ3 (only with the 1/50 or slower). At the HSSspeeds the user has to set it manually and this is quite easy and fast.
No the HSS is not usable with mechanical-shutter  Leica’s. The flash expects to receive specific electronic signals for proper functioning and the mechanical shutters do not have this signal. 
The finder.
The finder itself is not changed and all three versions (magnifications 0.58, 0.72, 0.85) will be available. The shutter indications have variable brightness dependent on ambient light levels and are very clear but also very civilized: they do not distract as they are positioned normally just outside the visual area of the user. The accuracy of the finder is very high and till 90mm not challenged by the reflex camera. I would note that even the 135mm can be focussed more accurately as the M-rangefinder uses the principle of visual acuity that is more accurate than the contrast based  principle of the groundglass focusing.

Everything can always be improved. The finder windows have an anti-reflection coating that diminishes clearly the flare of the rangefinder patch that occurs in some situations when strong light sources  are shining  obliquely into the finder.                      
The mechanical parts.
The shutter has been improved and changed substantially. In addition the top cover is now machined out of one piece of brass. The slow speed geartrain is gone, but electronics have been added. The total weight has been increased to 610 grams (10 grams more than the M6TTL) and the Leica R6.2 has a weight of 625 grams. The weight of the M7  adds to the stability when using slow speeds and is also an indication of the solidity of the engineering and the ample use of steel and glass. M3 cameras from 1954 are still functioning perfectly after more than 50 years of use.  They have a working life of at least 50 years and with some care will function for the next 50 years too. The M7 would be able to function till 2102 at least. That would cover three generations of photographers. The shutter is designed for 100.000 pictures before showing any sign of wear! You can shoot 2700 rolls of film before you could detect any tear or wear in the moving parts.
There is additional room in the body to accomodate two batteries and not the one battery in the M6(TTL). Both batteries are above each other.         
The Leica camera has a well-deserved reputation for longevity, engineering excellence and reliability. That does not imply that a new camera can never malfunction or even has some manufacturing defects. Sometimes the occurrence of these faults has been used to support the view that the current products from Solms and Portugal are not as reliable or manufactured to the same high standards as when the M3 was made in Wetzlar.
Based on a study of the production methods, material selection and material treatment, the assembly and quality control in Portugal and Solms  you are entitled to a very high level of expectation about engineering quality. On the other hand we should realize that the camera is mainly manually  assembled by highly motivated individuals, but where humans work, humans will inevitably make mistakes, however tight the inspections and quality assurance.
The rangefinder landscape.
What is the position of the M7 in the rangefinder landscape compared to Hexar RF, Contax G2, Bessa-family and the M6TTL?
The M6TTL is almost identical to the M7, but without AE, the improved shutter and the coating of the finder windows. But the M6TTL has the fully mechanical, battery-independent shutter and a lower list price. The Hexar RF lacks the TTL function, has the integrated motor/shutter assembly with a topspeed of 1/4000, and a very fine finder, but with a very detracting array of lights and symbols in the finder area. The RF has a very significant time lag too. The linup of lenses is small, but very good and the new 21-35 zoomlens with two fixed psitions is quite interesting. The motor has the additional role of compensating for the time lag, which is not the best way for the decisive moment style of photography.  The Hexar is a most interesting camera,that tries to be a bridge between classical and more casual styles of photography.
The Contax G2 has aspirations that are quite close to the ones of the Hexar (same shutter assembly, same type of body), but use Af as the bridging function Here we find a zoomlens from 35 to 70mm that can be set at all positions. The finder of the G2 is the worst part, as is the manual focus. The AF however compensates for the finder.
The Bessa R and R2 are made from a mix of an slr chassis and the CL-type finder. The chassis offers exposure  metering, set manually as with the M6(TTL). The CL finder is limited in its functionality and accuracy. Whle the specs are impressive, when related to price, the assembly of two separate philosophies is not convincing. The Bessa, while delivering the goods for a surprisingly low price, lacks character.
To sum up.
The M7 is an important  mark  in the history of the Leica. The integration of electronic exposure automation in the classical body shape, gives the experienced Leica user a smooth migration path and transition to even better photography. You need to give yourself the mental space to reflect on Barnack’s  ideal of a fast, effortless, intuitive and compact high quality camera.
When you get used to the M7 will forget about the manual exposure. Photography with the M7 is a joy and a very pleasant and relaxed way of picture taking. I noticed that I started to make more pictures  than with my M6, especially in conditions where you have trouble to react to quickly changing light levels.  Often you do not take the picture of a fleeting moment as the correct exposure takes some time and then the moment is gone already.
With the exposure automation, TTL function, the HSS add-on and the classical feeling and use of the M6, the M7 covers a very broad spectrum of photographic possibilities.
The illustrious predecessors of the M7.
The Leica 0-series.
Leica is the only manufacturer, that sells the first product from 1924 in almost identical shape and specifications. As if Ford would still have the T-Ford in the catalogues. Who wants to know what is was like to take pictures with the original Leica and to taste how people were involved with photography 75 years ago,  can buy/use the current 0-series. Here we have the Barnack-camera, as the master-designer has created it. A very compact camera with a minimum number of features and functions, and an extremely high level of mechanical precision. Next to the 0-series, the M7 looks big, but shares the same feeling. Inside the camera, there is hardly anything. A shutter with two non-capping curtains, a transport drum, a release button and shaft, and a rewind mechanism. The Leica was designed for fast and quick picture taking and the transportknob is incredibly smooth and without resistance. If you ever want to feel high precision engineering at its best, try to advance the film in the 0-series.
The practical use.
The Leica 0, lens and finder closed fits into a pocket of the then ubiquitous jacket or coat. With a weight of 465 grams (lens included), and a feline shape and feeling, (every part and shape of the camera is smooth and rounded), handling the camera is a joy. To take a picture you pull out the lens, and open the two part finder (a fold down window with a negative lens and a folding peep-sight). The shutter is tensioned with the rubber cap in front of the lens (to prevent light reaching the film). Shutter speeds are from 1/20 to 1/500 and can be set only when the shutter is in a certain position, indicated by an index mark on the speed dial.  It is best to set the shutter before making the picture and tensioning the shutter.  You look through the finder with the camera held at a distance of 25 cm from your eyes. This was a familiar act in those days. Most cameras were operated away from the face. The later development that the camera becomes an extension of the eye is a true revolution in camera design. Most digital cameras are also used from a distance to look at the display.
This is the routine: open finder and pull out lens, guess exposure and distance, take away lens cap, hold camera at 25cm distance, select and frame subject, press release button, put lens cap in front of the lens, transport film and tension the shutter.With some experience it works faster than can be described.
Essential difference with the M7 is the pure and dedicated attention to the core business of the photographic process. Guessing the distance and exposure, the deliberate decision of the aperture/speed combination that is needed in this situation and the careful framing of subject and timing of the picture in anticipation (no second chance) are required to complete the photographic act. We do it intuitive now, but then it was a conscious act. Being involved with the process in such a way is back to the roots and it gives additional meaning to Cartier-Bressons decisive moment. The excitement and expectations that people must have experienced when makingthose valuable pictures returns. The magic of photography as the art of fixing the shadows returns in the blood.
Photography with the Leica 0 is like being in a monastery for contemplation and to reflect on your inner self.
Photography started as a mechanical process to reproduce accurately the world around us. With the 0-series you know why that was exciting and rewarding.
The Leitz Anastigmat 1:3.5/50mm is a new design that in its capabilities challenges the Summicron-M 1:2/50mm. It is, like the predecessor, a 4 element lens, but now the aperture is symmetrically located between the second and third lens(group).
With aperture 6.3 you have some latitude in guessing the distance as at 3meter you have depth of field from 2.43m to 3.94 meter. Guessing the exposure is made easy as there are only 5 speeds to choose from (1/20, 1/50, 1/100, 1/200, 1/500). There are 5 exposure types from clear sun to dark and clouded and you need to memorize the shutter and aperture settings for each of them.  The Leica photographer had to stop taking pictures when the light is down to aperture 3.5 and speed 1/20. Here too starts the really difficult guesswork for the exposure. Leica photography is the catching of fleeting moments from strange perspectives with a handheld camera, crossing the dividing line between documentary and surrealistic photography. That is true Leica photography and the 0-series started it all.
The M3.
Thirty years after the 0-series, the M3 arrived on the scene (1954). A true revolution it was. A radical departure from the then reigning III-series: crystal clear 1:1 finder with frame lines from 50 to 135mm, finder and rangefinder combined, bayonet coupling for lenses, advance lever, it took the world by storm. This masterly design by Herr Stein is not based on the Leica IV as is often reported, but an independent construction by Stein, created in 1943. The camera was so new and advanced that it would have taken the competition several years to catch up. As the rangefinder market was already under attack from the slr camera, the competitors (Zeiss, Canon, Nikon) decided to jump on the slr bandwagon.
With high-speed lenses, and shutter speeds from 1sec to 1/1000 and an extremely fast rangefinding mechanism, the M3 evolved into the best camera for dynamic and close range human interest photography. But landscapes, portraits and even glamour (Hollywood) were part of the Leica domain.
The M3 is still a utterly useable and very capable instrument. In fact the M2, M4, M4-2, M4P and even M6 are simple extensions from the basic body. M6 has internal exposure metering, but that was already available in the M5. The M3 was a revolution compared to the III-line. And the M5 was a radical departure from the M3 family.
The Leica M5.
With the M4, Leica has maneuvered themselves into a corner without growth potential. Small improvements were possible, and the external coupled exposure meter, was not the best nor an elegant solution to the growing demands for easy exposure metering. The M5, from 1971, tried a novel solution and departed from the family line. There were many revolutionary changes in the M5, including the famous two flat retainers for the shoulder strap, the metering though the lens with a moveable metering cell in front of the film plane, and a shutter that could function till 30 seconds. The smooth top cover with the large speeddial that could be adjusted with one-finger, the smart indications in the finder, it all added to the concept of a new era in rangefinder design.
Mechanically the M5 was superb and functionally very impressive, as Leitz had used all the experience of 50 years of mechanical engineering and rangefinder expertise to create the M5. The disappointment that the M5 did not move the market as the M3 had done, killed almost the company. As with the R8, the M5 is a user camera and a very convincing one. It is not a design beauty. The flat topcover, the location of the transport lever, the front of the rangefinder area, it all gives the camera a somewhat squatted look. Functionally it is one of the best Leicas ever. Form follows function, was the idea in Wetzlar in those days. But the elegance of the M3 was lost. The M5 was functionally the better product. With the M5 ended the Leitz hegemony in rangefinder camera design. The successors, including the M6, returned to the M3 roots. The new M7is again a radical change from the current line. And so the M3, M5 and M7 are from this perspective the real milestones in the M line development.