Simulations of additive projection systems.

The most difficult simulations to achieve are the early additive projection systems that are now often restored by printing onto modern colour print film via modern colour negatives or intermediates.

The originals either were three separate projectors, or the sequential projection of three separate images through red, green or blue filters, or were two records treated in this manner.

Either the filters were over the camera lens or were dyes applied to the film, by conventional tinting. Very few technicians or archivists have ever seen original material projected this way, although, in principle, it is not difficult to do. The early colour filters were at least as good as those produced today - the modern Kodak Wratten tricolour filters used for original photography as well as for the projection, Wratten 25, 58 and 47B are the same today as those made in 1910.

A modern additive system is relatively easy to produce along similar lines to Kinemacolor or the sequential frame systems, but a still additive image is very easy. Three still negatives are made of a scene, on panchromatic film, through the three tricolour filters, and prints are made. These are projected in register on a single screen and the three filters put over the lens. The relative projector brightnesses may need adjusting using neutral density filters, but providing the contrasts of the three separations are similar, a very high quality colour record is produced. This suggests that the primary problems of early additive colour were not the quality of the image but the complexity of the equipment needed to project synchronously and in register the three images. In the case of sequential images, this had to be done at three times the normal projection speed to reduce the flicker.

1. Unfortunately, many modern simulations are lacking in the colour quality that must have been present in the early additive systems, probably due to several different effects.
2. The sequential frame systems were often tinted frames and these dyes fade - copying on modern colour internegative film simply copies the faded colours.
3. Red, green and blue filter primaries were very saturated and even ideal subtractive dyes cannot encompass these saturations.
4. The subtractive dyes used in modern films have notably poor cyans that are darker and less saturated than they should be and magentas that are darker and bluer than they should be. Above all, our expectation of the quality of these early films is probably too low, and we fail to recognise the degree of correction we need to apply.