Colour Grading.
Sight grading is almost impossible with the modern masked negative, but was used before the introduction of the analyser, especially for unmasked negatives prior to 1955. In general, early grading was by test strip or by trial and error.
Pre-grading
Most grading is negative-positive, but some reversal positive camera films
were also printed onto reversal print film. In this instance, a different
procedure can be adopted from the sight grading, which was just educated guess
work, or the use of test strips. The procedure was known as
"pre-grading" in some laboratories, and is still in use today. Since
both the original and the reproduced print are positives, the printing
conditions are set up so that a print is produced that matches the original as
closely as possible and these filtration and/or lamp conditions become a
standard.
The grader views the original before it is printed [on a light box or by
projection, and estimates the filtration or exposure needed to correct the
original to what is wanted - if no change is needed the printing conditions are
left at the standard.
The procedure works as well with colour as with black and white. The exposure
changes can be assessed by laying neutral, or coloured filters in the case of
colour, on the original on a light box, and these same filters are more or less
what will be needed to correct the print.
Re-grading
This is the procedure of making a correction to printing conditions based on a printed result in an Answer Print or a test strip. This is usually by sight, even after an analyser was used for the first print. Many black and white graders rely on their experience and judgement to make these final, usually small, corrections, but many colour graders use filter aids. A gelatine colour filter laid over the top of a print can help to see the effect of a printing correction. The filters used are usually Kodak CC filters that come in a range of colours, R, G, B, C, M, Y, and a range of densities from 0.025 to 0.50. These are the filters used for subtractive printing. The value used for the printing correction is half that of the filter needed visually [because of the increased contrast of the print stock]. If the printer is using additive light valves, the halved filter value is converted to additive printer points at the conversion of 1 Printer Light equals 0.025 Log E.
