Subtractive Color Printing

[tgtaylor]

Can anyone offer an explanation of why you add to the value of the complementary on the enlarging head when you really want to subtract it from the print?

In other words, suppose at 45CC of yellow your print looks a little too blue. Since yellow is complimentary to blue, adding yellow will block blue. So let's say you want to add 10CC of yellow to the next print. Common sense would have you dialing 55CC yellow on the enlarger. But doing that would only subtract 10CC of yellow. Instead you would dial in 35CC yellow - which appears contrary to common sense.

Got an answer?

Thomas

[Nick_3536]

Why does adding more light make the print darker not lighter?

[Gene McCluney]

Why does adding more light make the print darker not lighter?

Because print making from a negative is a negative/positive process. When you add more light to your exposure of a print (color or b/w) the silver grains get more photons, hence they develop quicker and form larger clumps, producing a darker silver image. In color the more exposure does the same thing, and in addition the color couplers release more dye, thus your dye image is darker in the final print. (The silver image is bleached out in the final color print).


By comparison, when you shoot a slide (reversal process) when you open up you are giving more light to the negative stage of the process, producing a denser negative, leaving less silver for re-development into a positive, thus a lighter positive.

[Gene McCluney]

Can anyone offer an explanation of why you add to the value of the complementary on the enlarging head when you really want to subtract it from the print?

In other words, suppose at 45CC of yellow your print looks a little too blue. Since yellow is complimentary to blue, adding yellow will block blue. So let's say you want to add 10CC of yellow to the next print. Common sense would have you dialing 55CC yellow on the enlarger. But doing that would only subtract 10CC of yellow. Instead you would dial in 35CC yellow - which appears contrary to common sense.

Got an answer?

Thomas

The simple way to think of this is a filter "blocking" its color of light. The more you dial in the filter the more you block (SUBTRACT) that color. By letting more yellow through (for instance) by using less "yellow blocking" you are in effect getting more yellow in the print. By just allowing more yellow, you still will have to make an exposure correction to keep the print from going darker, assuming the density of the print was OK already.

Nomal color printing-color prints from color negatives, one just uses the Yellow and Magenta channels to adjust those components to balance with the Cyan. Only in extreme cases would one use all three, because if you have any amount of all three filters dialed in you are creating neutral density and that means longer exposure times.
If you get a good print with (for example) 5cc Cyan, 10cc Yellow and 15cc Magenta, then you can subtract 5 cc from all three channels and get exactly the same color balance, which would then be 0 cc Cyan, 5cc Yellow and 10cc Magenta. The image on the easel would be brighter, so you would then compensate in your overall exposure time or aperture.

[Drew Wiley]

What are you intending to print? There is a complete difference printing black-and-white negatives using a colohead, printing color negatives, and printing chromes onto a
positive paper. Subtractive colorheads also behave differently than additive ones. I am
familiar with all the above. But in general it is a mistake to think that so many cc's of
a given filtration will correspond directly to the same amount of change in print density. It's a lot more complicated than that, since paper response is rarely linear.
But in practice, a few moments with a test strip can save you years of speculation.

[Curtis Lowe]

The simple way to think of this is a filter "blocking" its color of light. The more you dial in the filter the more you block (SUBTRACT) that color.

But when you dial in more yellow, the light shining down on the paper also looks more yellow so how does that reduce the yellow in the print?

[Gary Beasley]

Because yellow light from the enlarger makes blue on the print, the compliment or "negative color" of yellow.