Colour Printing.
Colour Printing in the past covered a wide range of techniques and stocks,
but since about 1960 has implied the printing of colour negatives onto colour
print stocks, or reversal positives to reversal positives where both films are incorporated
coupler integral tri-packs. These materials are the basis of all present day
printing for modern film production as well as for the colour restoration of
archive colour film.
Subtractive Colour printing
The subtractive system is so called because white light is used as the printing light source and subtractive colour filters in the beam modify the red, green and blue components of the light. Cyan filters reduce red light, Magenta reduces green light and Yellow reduces the blue light. The cyan, magenta and yellow filters are made in different strengths and described by their density to red, green, and blue light. The weakest filters available have densities to their complementary colour light of 0.025 that corresponds to one printer point on the additive light valve system [see below]. The different densities of filter available are 0.025, 0.05, 0.10, 0.20, 0.30, 0.40 and 0.50 in the three subtractive primaries and in the three additive primaries, red, green and blue. With this combination, it is possible to make up any colour combination up to 0.50 in a maximum of three filters.
The Kodak filters for this purpose are designated CC [for colour correcting] /the density/the colour; so for example, CC50Y and CC05R, correspond to 0.50 density to Blue [a yellow filter] and 0.05 density to Cyan [a Red filter], respectively. Subtractive printers have filter positions in draws or slides positioned close to the condenser lenses or the filters are mounted on Waterhouse stops mounted at this position.
Additive Colour Printing
The additive system consists of exposing film to controlled amounts of Red, Green and Blue light each separately controlled in intensity to create the exposure and colour required.
Almost all light valve light sources [see above] used on modern printers today are for additive colour printing, but can equally cope with black and white, by varying the R, G, B light settings uniformly.
The lamp house has a single light source and a beam splitting arrangement into three separate light beams. The three separate beams are passed through filters or reflected by dichroic mirrors to produce separate red, green and blue beams each controlled in intensity by a light valve. Dichroic mirrors are used in preference to filters, as there is less light lost.
Thus the three separate light valves need three sets of printer point information at each cued change. Composite punched tape therefore carries cue data, and the red, green, and blue printer light values.