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Unlike the commonly accepted wisdom, development times for different papers and different photographs do vary.
This is for many reasons including the type of paper, the make, the grade (even with multigrade), and of course, the actual photograph itself. Basically, longer development will increase contrast (just as with the film) and shorter development will decrease contrast or flatten the image. As Ansel Adams pointed out, this phenomena can be used to our advantage to fine tune our print. He called it Factoral Development and you know something? It really works....
First, it's important to realize, that test strips are treated differently than our print. Because of the many variables of exposure, we have to standardize our test strip time. For the test strip we would always use 2 minutes development. I even use two minutes for developers that suggest less time (Ilford Multigrade developer for instance).
This is important because if we start messing with our test strip development time we will be changing the print density through development instead of through the correct variable at that point, the exposure.
Once the basic exposure of our paper has been ascertained from these test strips we can use the factorial method for finding the best developing time. This will achieve optimum results and is very easy to do.
How to ascertain the Factoral paper development of your print
This is done after you have used test strips to work out the print exposure time. Using the correct exposure time, watch as your print develops for a detailed mid-tone to begin to appear. As soon as you see it starting to show, note the time elapsed since you started development. You then multiply this appearance time by a number we call the factor.
Initially, try developing for a time factor of 5.
- For example, if a mid tone appears at 30 seconds, develop for a total of 2 ½ minutes (5 x 30 seconds).
If the mid-tone takes 40 seconds to appear then develop for a total of 3 minutes 20 seconds (5 times 40 seconds). Remember to use the same mid tone area for each repetition of that print.
A factor of 5 is a good ballpark figure to start with. If after drying the print (and you must dry the print), you think it is too flat, increase the factor by one (you can go up to a maximum of 8). Increasing the factor increases the contrast.
If you still have not reached the level of contrast required, and you have reached a factor of eight, increase the paper grade and start again at factor 5. If the print is too contrasty then lower the factor down to a minimum of 3. Lowering the factor decreases contrast. If it is still too contrasty then drop the paper a grade and start again with a factor of 5.