I spent my darkroom time last night on split contrast printing with my color head and the difference is amazing! My negative are usually quite contrasty, but between the 4x5 neg and the split printing I'm getting extremely smooth skin tones. It took me a while to get it right (I was also trying to mess around with fstop printing, but became so befuddled I had to call it a night not to mention my homework). The difference is so great that I've even decided to use the portrait (more a 4x5 headshot) as my next postcard... I've been having trouble deciding what I should actually send.
Okay, now I am confused. Les yousay yellow doesn't work to soften contrast but then you say you use a 70 yellow???? Anyway, I have found all of the old contract filters that were used to assist in halftoning and the "add contrast" filters are varying densities of magenta and the "lower contrast" filters are all shades of straw or yellow if you will.
But, what I don't get is the whole split filtering concept, here. Are you applying a filter then shading out the parts that you don't want effected by that filter, applying another filter and exposing the parts you were just shading?
As for theCMY vs RGB, cyan opposes Red, yellow opposes blue, and magenta opposes green. The problem with trying to discuss these things is. . . What color is yellow to you may not be the right yellow as far as photography is concerned. I have been fighting with this concept since I have been trying to incorporate color into the shop without a dichroic head. I have reverted to terms like cherry and salmon rather than red, because although they are both red; cherry brings up green in negative printing, while salmon brings up cyan. Straw yellow brings up a colbalt blue, while lemon yellow brings up more of a lavendar or indigo blue.
Anyway, I would like to understand this whole split contrast filtering concept. AND I wonder is it applicable to color or just b&w. I have been trying to find a way to adjust contrast in color, but so far I only adjust the color, not the contrast. Or with the neutral density filters, I simply change the exposure time but the image remains about the same in the end.
[quote="Darkroom ChromaCrafts"]Okay, now I am confused. Les yousay yellow doesn't work to soften contrast but then you say you use a 70 yellow????
You've missunderstood the comment, IMO 70 yellow is the optimum value to use for soft filtration. Increasing the value, to say maximum yellow, will produce very little more "softness" but will mean that you have increased the density which will need more exposure.
The matter of split contrast filtering is applicable to black and white variable contrast materials. It does not apply to fixed contrast (graded) black and white papers.
With variable contrast materials there are two separate and distinct characteristic emulsions. One is primarily affected by yellow or green and the other is affected primarily by magenta or blue. (The reason that I listed pairs of colors is that some variable contrast light sources use subtractive and some use additive colors. In the case of Lee's aristo cold light head he filters with blue and green. In the case of my Saunders I use magenta and yellow. Magenta and blue are the colors that affect high contrast and the colors of yellow and green affect low contrast.
Normally printing on variable contrast paper is done by varying the ratio of one light color to the other and this arrives at an infinitely variable grade (within the confines of the papers limits).
In the case of split contrast printing the printing is separated into two distinct exposures with one being a soft contrast exposure and the second being a high contrast exposure. One of the advantages of this type of printing are that burning and dodging is more controllable within the two exposures. In other words if I wanted to dodge a shadow area, I would due this during the high contrast exposure since this is the exposure that affects primarily the low values. If I wanted to burn a highlight down, I would do this during the low contrast exposure since that exposure affects primarily the lighter tonal values. Additionally, I feel that I am able to arrive at the correct contrast on the print more rapidly then if I am choosing a single contrast setting.
To summarize, instead of printing a negative at, for instance, 20 seconds at grade 2.5(in a single contrast setting on variable contrast paper)...I may end up doing a 10 second exposure at grade one and a second exposure of 8 seconds at a grade 5.
To expand on Les's explanation. The optimum (maximum effect) of the yellow filtration is 70 units, in his experience. He is saying that to add 120 units, for instance, will do nothing more then 70 units except to add density to the light path and therefore increase printing exposure time.
Hope that this explains this for you. Please feel free to question if you do not understand.
Actually yes it does. When Jeremy said he was getting smooth skin tones I was hoping he meant color.
I didn't understand why variable contrast works the way it does. Your explanation is excellent. Now I can incorporate that into better outcomes as well. Thank you very much. You should open a school, you teach so well.