Apple Color 1.5 - Manual (Page 250)

Printer Points Controls
These parameters are available for colorists who are used to working with the printer
points system for color timing film. Employed by film printing machines, the printer points
system allows color correction to be performed optically, by shining filtered light through
the conformed camera negatives to expose an intermediate positive print, in the process
creating a single reel of film that is the color-corrected print.
The process of controlling the color of individual shots and doing scene-to-scene color
correction is accomplished using just three controls to individually adjust the amount of
red, green, and blue light that exposes the film, using a series of optical filters and shutters.
This method of making adjustments can be reproduced digitally using the Printer Points
parameters.
Tip: These parameters are controllable using knobs on most compatible control surfaces.
What Is a Printer Point?
Each of the Red, Green, and Blue parameters is adjusted in discrete increments called
printer points (with each point being a fraction of an ƒ-stop, the scale used to measure
film exposure). Color implements a standard system employing a total range of 50 points
for each channel, where point 25 is the original neutral state for that color channel.
Technically speaking, each point represents 1/4 of an ƒ-stop of exposure (one ƒ-stop
represents a doubling of light). Each full stop of exposure equals 12 printer points.
Making Adjustments Using Printer Points
Unlike virtually every other control in the Primary In room, the Red, Green, and Blue Printer
Points parameters make a uniform adjustment to the entire color channel, irrespective
of image tonality.
Also unique is the way in which adjustments are made. To emulate the nature of the
filters employed by these kinds of machines, raising a parameter such as the Printer Points
Red parameter doesn’t actually boost the red; instead, it removes red, causing the image
to shift to cyan (the secondary of green and blue). To increase red, you actually need to
decrease the Printer Points Red parameter.
Increasing or decreasing all three Printer Points parameters together darkens the image
(by raising all three parameters) or lightens it (by lowering all three parameters). Making
disproportionate adjustments to the three channels changes the color balance of the
image relative to the adjustment, altering the color of the image and allowing for the
correction or introduction of color casts.
250 Chapter 9 The Primary In Room