The creation of a negative developer is one the one hand very simple, because the active components are known for a long time. Changing the relative proportions of the chemical parts does change the characteristic and behavior of the developer. A careful and diligent worker can mix his own solution and there is evidently a small market for this activity as one can buy the necessary chemicals in several shops. High-quality developers with consistent performance are not easy to create. The basic facts of the behavior of the chemical components may be known, but the actual chemical interaction is not a simple matter. Considerable knowledge of the theory and practice of the chemical reactions in different environments is required and this knowledge you get only after a long time.
Classic developers, examples Kodak D-76 or Agfa Rodinal are on the market for almost a century or even longer and they still work quite fine.
And for the traditional darkroom they are still commendable and produce excellent results. The competition with high-grade inkjet printers cannot be neglected and it is true that there is a convergence of quality in the area of fine printing on inkjet and on silver-halide papers. It is clear that the domain of large prints (above A3/A2) belongs to the digital printer. Such large prints are almost impossible to handle in the home-darkroom. And to be honest: the negative may be of outstanding quality, but an enlargement (from a 35 mm negative) of more than 10 - 12 times will degrade the image quality because of grain and light scattering. The creation of a sharp print with good tonality is no longer enough to bring out the best of silver-halide printing.
It was customary in the past to have a range of films and a range of developers to match the desired characteristics. This approach was quite flexible, but required that you were a proficient photographer and a heavy user because chemicals did deteriorate quite fast.
One important company that is dedicated to exploit the limits of chemical processing is Spur, owned by Heribert Schain. He and partners have promoted the use of high-resolution microfilms and the combination Spur Orthopan UR and Nanospeed UR is my favorite choice when the maximum definition is required. At this moment I achieved 160 linepairs/mm with the best Leica lens available for M-use.
Mr. Schain created a new range of chemicals that are claimed to deliver unique results. The first practical claim for the new high dilution Acurol-N is the longevity. Acknowledging that the amount of films that one develops per month is dropping, the developer has an extended lifespan. The dilution is very high (generally between 1+50 and 1+100) which allows a very economical use and a very flexible use. In this sense the developer shares one characteristic with Rodinal: you can vary the dilution and use it for almost every film emulsion. Development times range from ten to thirty minutes (with exceptions on both extremes) and the longer development times demand the method of minimal movement. Especially this last characteristic is important because this method enhances the edge sharpness (Eberhard effect), increases visual plasticity and also enhance grain impression slightly. The nice point is of course that one can vary the parameters within reasonable limits with one developer for a range of films and contrast situations. Good news for Zone System workers.
I used the developer with the evergreen film Ilford Delta 100 (still one of the best all-rounders for medium speed use), exposed for EI 80 and developed for thirty minutes with the Heiland TAS developer equipment (excellent for long duration and minimal movement). As a companion I used the new Adox Silvermax film. Camera is Leica MP-3, grey card is from Fotowand whose cards are of superior quality, exposure meter is Gossen Digisky.
The results are excellent. One does not often see a density of Dmax = 0.06 in Zone I at normal ISO-speed and development.
The graph below is illustrative for the potential of the film/developer combination. The almost identical CI of both films are an indication of the compensation qualities of the developer.
The high densities in the Zones VIII and IX are not important for normal work, but they indicate that zone system N+ and N- are possible by changing development times.
The long development do increase the grain, but at a ten times enlargement it is still very pleasing. See picture below (selection of full negative).
The high acutance can be seen in this shot (a selection of the full negative). Note also that the edges are very clean and do not show the familiar softening of the digital image because of color fringing.
The attainable resolution (test chart under microscope) is situated between 60 lp/mm (Silvermax) and 80 lp/mm (Delta 100). This compares well with the Leica M9 camera and the Leica M Monochrom.
The Acurol-N developer is a major improvement for the darkroom workflow and should be a premium choice for anyone who is engaged in the silver-halide workflow, exclusively or in a mixed fashion, selecting the workflow that is best for the desired result. The data-sheet has all info for fine tuning the Zone System parameters.