(4) The filter pack should not contain more than two colors of the
subtractive filters (yellow, magenta, and cyan). When all three colors are
in the filter pack, the effect is neutral density which only serves to
lengthen the required exposure time.
(5) Neutral density is eliminated by removing the filter of one color
completely, and then removing the same density of each of the other two
colors. For example, assume the filter pack you came up with was 46Y + 38M
You would completely remove the cyan filtration plus 12Y and 12M.
Thus your adjusted filter pack would be 34Y + 26M.
printing color negatives, printing color
transparencies takes a greater change in filter pack to accomplish the
c. Exposure Adjustments.
Whenever you change the filter pack,
allowance should be made for a change in exposure caused by the change in
filtration action, and the change (if any) in the number of filters.
allowance for these changes is not made, the density of the reprint will
differ from that of the test print.
Figure 5-2 gives appropriate filter factors which will help you calculate
the correct exposure.
Filter factors for CC and CP filters