U of S | Mailing List Archive | alt-photo-process-l | Re: another 3 layer gum attempt

Re: another 3 layer gum attempt

On Jul 21, 2009, at 9:24 PM, Katharine Thayer wrote:
I hope my instructions didn't get you off track; if so I may need to look at that page again. The point I was trying to make there was that if you expose for DMax alone, you're going to underexpose for gum, because you'll get DMax before you get the optimum number of steps retained, but obviously you don't want to take that too far. If you settle on a standard development time it shouldn't take more than a couple of wedges to nail that down.
For most colors it's true, as I showed in my demonstration with a red (PR 209, as I recall; I'm too hung over from the Everclear to go look it up) that you'll get DMax before you get to the optimal exposure, as shown by the fact that the DMax and color saturation at 1.5 minutes exposure is the same as the DMax and color saturation at 4.5 minutes exposure, though the optimal exposure that gave the most number of steps without pushing the steps up the wedge was 2.5 minutes. One of the purposes of showing this set of wedges was to illustrate the point that you can't get more DMax or color saturation by more exposure beyond a minimal point; the DMax and color saturation for a particular coating mix are what they are. As I said, this principle works for most colors, but obviously not for yellow; with yellow more exposure does continue to push DMax and color saturation into an unwanted territory, as Paul has discovered. I'll have to add another paragraph to that set of instructions to deal with yellow.