Page 118 - Graphic Design and Print Production Fundamentals

4.7 Profile Creation

Alan Martin

Figure 4.9 what is a profile

The measurement file contains the raw data of the relationship between the device dependent colour
space of the device and the device independent colour space of the profile connection spaces (PCS).
There are two additional parameters we have to provide along with this data in order for the colour
management software to produce an output profile: total ink limit and black generation (see Figure 4.9).

Total Ink Limit

Total ink limit is a percentage, usually between 240% and 400%, that represents the upper threshold
that the sum of the four process inks can total. Why would this change? Each device, in combination
with its particular substrates (papers) and ink sets, has a different capability in terms of how much ink
can be deposited. A coldset web newspaper press might be close to the lower end of 240%, while a
high-end inkjet can support 100% from each of cyan, magenta, yellow, and black, and have a 400%
rating. This total ink limit setting affects the colour distribution in darker colours. As the total ink limit
decreases, dark colours require a higher proportion of black ink relative to CMY to stay within the ink
limit percentage. With an ink limit of 360%, when black is at 90%, we still have room left for 90% of
cyan, magenta, and yellow (4 x 90 = 360). But if the ink limit is 240%, with black at 90%, we can’t
exceed 150% for the sum of the other three (150 + 90 = 240). Since cyan leads in a grey balance mix,
we might have 60% cyan, 45% magenta, and 45% yellow (60 + 45 + 45 = 150). As the ink limit drops,
black has to do more of the work of providing darkness for any heavy colour mix.

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