Tricolour – Filters etc.

Photographing a scene in colour using Tricolour doesn’t need much over & above any other black & white photography. The film has to be panchromatic, the camera absolutely has to be on a tripod, and the really important extra items are the separation filters.
Generally these will be the set as defined by Kodak, the Wratten filters;
Red – no. 25
Green – no. 58
Blue – no. 47B

The graph of way they cut the spectrum into 3 parts;


You can see there’s a bit of overlap between the regions, which is not wholly desirable, but it keeps the ‘speed’ higher. There is another set of steep or narrow-cut separation filters, including Wrattens 29 (red) 61 (green).

Kodak don’t really offer much in the way of Wratten gelatin filters now, but most of the important ones are available with a polyester base in the Lee range;


Although for the highest quality & saturation the normal tricolour set is desirable, it’s possible to get away with all sorts of liberties when experimenting.
‘Quality Street’ chocolates come wrapped in a variety of coloured acetate foils, & it happens that there ‘s a competent set of separation filters in there;


Mounted up in black card slide mounts for ease of handling. By no means optical quality, or good spectral crossovers, but as long as the spectrum is chopped into 3 sectors the resulting negatives will do the job.

The routes to making separation negatives are well defined in this old diagram;


… but we’ll discount the one-shot camera, and the integral tripack as proffered with Ektachrome & Kodachrome, as the only one we’re interested in here is the ‘conventional camera ~ three exposures’ route.

Three exposures are made of the scene, one using each filter. It goes without saying that the quicker one is on the draw, i.e. switching filter & preparing for the next shot, the more controllable the environment will be, especially if trying to make a landscape picture.


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