Tricolor Exposure Method

A Post In Three Parts

this is the first post. starting steps.

Bad Names

Additive and Subtractive printing.

by modifying the color of light, we affect the color of the print. Simple enough.

The photograph is an illusion which stands in for something else. If done well enough, the magic occurs; sometimes reproducing reality, while others replacing, or replenishing it.

the most consequential artists of the past 100+ years have asked their questions using the language of color.

Two Modes of color printing: white light, or additive (tricolor).

dslr is an electronic one-shot tricolor camera.


A small cardboard box with plastic exposure wheel and a color wedge calculator. This was probably the most used hobby way to color printing. It also probably caused more people to try, then leave color darkrooms. The real heritage is the mass of drums and rotating bases filling landfill and ebay. [Canadian company that made roller bases and tanks that he produced for several companies. With small detail changes they were marketed, at the same time, by Simmard, Unicolor, Beseler and Omega.]

filter wheel

Specialized Enlarger

Phillips PCS tri-one enlarger introduced in 1979; six years later, Beseler introduced the Minolta 45a at PMA 85. Both used primary color, aka, additive filters. These are narrow pass filters similar to the effect of using Wratten 70, 98, and 99 filters.

Phillips PCS
Minolta 45a

minolta 45a system


The Head is the light source that sits in the enlarger replacing the other beseler light source. It uses EU (exposure units) to control color and density of the print. These range from 0 to 250. Each 30EU is 30cc in subtractive filtration, which is a density change of 1 stop.

The Controller is the main portion of the unit. controller and head are connected by a cable which you do not remove. Take care not to kink or twist it much, since it is a fiber optic cable that can be broken without showing external signs. Once it breaks, you need to find a new complete system I use the 45a on a Beseler. It could also be used on an Omega D series.

My main use is to print color negatives. I also occasionally use it to make separations used in assembly processes. Kodak Pan Matrix film would expose well at 100,70,90 for Kodak Ektar film.

[ additional at private link]

RA-4 Color Printing

drum processing