Testing VC grade changes w/o change in exposure

[brian steinberger]

I'm looking to run some tests to find a mix of yellow and magenta on my dichro head to produce consistant exposure as I change grades. My question is, does anyone know of the easiest way to test for this? Using the least amount of paper possible would be nice. Or is there charts already made up for some sort of a starting guideline? Thanks

[Oren Grad]

The insert sheet that comes with Ilford papers lists suggested constant-exposure filtration settings. I don't know whether that's true for the other vendors remaining in the B&W paper market.

[robc]

you're going to wish you never asked that question..

http://www.butzi.net/articles/vcce.htm

or if you prefer the simple method then don't use both Y and M together. Just start with white light and dial in either Y or M.

If you are using Kodak dicroic filters then the additional density and therefore exposure adjustment is known. Someone should have a reference chart with exposure compensation times.

The same applies for durst filtration.

Problems can be that although your enlarger says it is dialing in 30 units it may not. But the fact is that if you are printing regularly then you will very quickly get to know how much exposure compensation to apply and it will be the same for all papers whereas the Y+M route requires calibrating for every paper or you will have to make exposure adjustments anyway in which case you might just as well use the second method anyway.

You can spend a lot of time trying to calibrate Y+M settings and never get it spot on.

[Oren Grad]

Per rob's comments, I should add that I don't bother with the constant-exposure settings myself - I just use straight Y or M, as needed. Even within a single printing session, you quickly get a sense of the exposure change needed to stay within the ballpark and minimize the number of useless test prints as you move up and down the contrast scale. Even if somehow I had a set of calibrated settings that preserved any particular print density across contrast grades, in most cases I'd still need to be making test strips or test prints because the exposure that preserves any arbitrary density isn't necessarily the one that's pictorially most pleasing as the contrast grade changes.

[Jay DeFehr]

I use Butzi's procedure, and I do have to repeat the calibration for each VC paper I use, but it doesn't take long once one gets the hang of it. My enlarger head(Beseler computerized color head) measures the light inside the head and displays the actual filtration value, and not just the indicated value, so filtration creep is not a factor for me. I find this the best method for using a color head to print VC papers. Dead consitent with no surprises at either end of the contrast range. For othe kinds of color heads that don't display actual filtration values, and represent an approximation, the precision of Butzi's procedure might be a waste of time, and similar results obtained by simpler approximations. Good luck.

Jay