A tale of three Developers,

AgX photography at this moment in time dwarfs in magnitude compared to the 700 million digital pictures that are uploaded on the internet day after day. It seems that the negative trend  for silver-halide photography has changed in a positive upward direction. The medium has the advantage that the final prints have a special tonal aesthetic that you cannot achieve with digital (inkjet) prints. As usual when human vision is involved there are many characteristics that have to be subjectively evaluated which makes discussions quite complicated.

Darkroom prints should not be enlarged too much. The best enlargement for 135 film is about 8 to 10 times. Then you have the optimum balance between size, grain and sharpness impressions and with an A4 format the quality of the print and the composition have to be very high. This poses a challenge for most Leica photographers. There is a simple calculation: the eye at normal distances can resolve up to 8 linepairs per mm. The maximum resolution of most medium speed films is in the range of 50 to 80 lp/mm and this fits the 10x enlargement factor. There is a common rule that a high-quality print with good sharpness is possible with a resolution of 2 lp/mm, when looking at a large print hanging on the wall. But an A4 print shows additional depth and plasticity when the textural detail is a very high order. 

The tests were made with Ilford 100Delta, a film with excellent balance of grain, sharpness and tonal scale. The alternatives are Kodak T-Max 100, Adox Silvermax and Ilford FP4. The Apo-Summicron-M 2/75 mm ASPH, stopped down to f/4 was used, on tripod of course and a range of exposures was made to see how the exposure effects the resolution. There is no reason for focus bracketing (the lens hardly exhibits this phenomenon and the thickness of the emulsion compensates for a slight shift). 

The film was exposed at EI = 64. The nominal ISO speed is quite useful, but produces negatives that are a bit too thin for most uses and I use the Leitz V35 with Heiland System that asks for some higher CI-value. 

The developers used are the newest version of the Spur HRX developer, the Spur Acurol-N and the Compard R09 which is comparable with the classic Agfa Rodinal. 

The dilution is: HRX 1+20, Acurol-N 1+100 and R09 1+50. 

In all three cases one should avoid over-exposure by more than one stop as this increases the grain and reduces the resolution in a significant way. On the other hand one has to say that every developer produces a crisp 40 lp/mm which even today is still the benchmark for high quality optics. 

The R09 has a resolution of 60 lp/mm, a fine grain with tight edges and a very even distribution. This produces excellent edge sharpness and up to A4 there is hardly any grain visible. The steep curve produces a pronounced and slightly compressed mid-tonal range, but the highlights are too dense even for burning actions. When one reduces the development times, one has to be careful to keep the shadow details in place. A very rewarding developer and because of its good shelf life a very economical one.

The Acurol-N has a resolution of 60 lp/mm, a fine grain with compact size and a very even distribution. This produces very good edge sharpness and up to A4 there no grain is visible. Scattering in the emulsion is very low and this shows up in the plasticity of the prints.The steep curve produces a pronounced and slightly compressed mid-tonal range, and the highlights are dense, but printable.. An outstanding developer with excellent keeping properties and also a very economical one.

The new two-solution HRX is a reformulated version with almost indefinite shelf life. It should be the first choice for darkroom users who shoot film at a moderate rate. The HRX has a resolution of 70 lp/mm, very fine grain that is very closely packed and very even distributed. This produces very good edge sharpness and up to A4 there no grain is visible. Scattering in the emulsion is extremely low and this can be seen at the edges of outlines.The shape of the curve produces a slightly expanded mid-tonal range, and the highlights can be printed without any additional burning. This is an excellent developer for Zone System users as it has a tonal range of 8 to 9 stops.  Again an  outstanding developer with indefinite keeping properties.

These developers have different characteristics and a user should be able to find one that suits the demands and equipment. There is still a haze of mystery around developers and their use. Most books warn that the developer time, temperature and degree of agitation must be within the narrowest of tolerances. In practical situations one may be more relaxed. Temperature must be closely watched, but all other parameters have their effects, but can be controlled in the darkroom. As always, one should test the material before doing an important assignment, but one test film should give you enough confidence to change the variables in the desired direction.  

The two Schain developers are the preferred ones for exacting demands. The HRX has the finest grain and the longest tonal range. The Acurol-N is a bit more grainy, but has the additional bite of the steeper mid-range. It is a choice between subtleties, but such is the world of AgX developers. 

The R09 has the classical virtues of flexibiliy of dilution and high sharpness. But the price you have to pay is visually pronounced grain and a steep gradation that limits the exposure latitude and you have to very careful not to over-expose.