Most alternative processes need a light source high in UV light, although many of them also have some sensitivity to light in the near UV, violet an blue. The stain of Pyro negatives functions as a very strong actinic filter to UV light and increase the effective printing contrast. Negatives developed in non-staining developers such as D76, HC110, etc. pass UV and Blue light about equally well.
Originally Posted by DrPhil
The dual-purpose is possible with stained negatives because the effective printing density is much greater for UV processes than for Blue sensitive processes. For example, a typical FP4+ negative developed in Pyrocat-HD for about seven minutes will have an effective printing density range of about 1.05 for Blue light but around 1.35 for UV light. You could print this negative on a grade #2 silver paper and also with a standard 25/75 mix of pt./pd. with just a small amount of contrast control.
Last edited by sanking; 08-29-2004 at 01:25 PM. Click to view previous post history.