Going back to the original question - because several of the answers contained either errors or confused language, I'll try and clarify:
Just received a third party process swatch book. In the book it lists the densities that the job was run at. They are:
K: 1.90
C: 1.45
M: 1.50
Y: 0.95
Are these standard numbers? If not, what are standard numbers, or is this simply to vague of a question?
They are close enough to the N America solid ink density targets - which are, for Grades 1 & 2 premium coated paper are:
Yellow 1.05 Dot gain (TVI) 18
Magenta 1.50 Dot gain (TVI) 20
Cyan 1.40 Dot gain (TVI) 20
Black 1.70 Dot gain (TVI) 22:
This is for 175 lpi - i.e. GRACoL 6/7- measured dry (not wet) values.
Some things to note.
SID is an indirect measure of ink film thickness. Coating the paper (or other substrate) with an even and consistent ink film thickness is one of the primary functions the press is designed to do and the press operator is trying to accomplish. But, it does not give you useful information about what color that ink is. So, for example, two patches of 100% Magenta can have equal densities but the hue of the color may be different. As a result, the color you get when you specify from your swatch book may be different than what you actually receive, especially if the swatchbook you're using did not come from your print supplier.
TVI (tone value increase) is/was an attempt to replace the term "dot gain" because it describes more accurately what is happening. I.e. TVI refers to the difference between a requested tone value (e.g. 50% in InDesign) and what that tone ends up being on final output (e.g. 50% in the file becomes 68% in the final press sheet). TVI, also gets around the problem of some devices not actually delivering a dot in the final output. Measuring TVI/dot gain is not dependent on the the halftone screening being used (AM, FM, etc.) because a densitometer (or spectrophotometer) does not "see" dots - it know nothing about screens. It just "knows" about what amount of light is sent to a surface and what amount of light is returned. Dot gain measurements include both optical and mechanical gain. As they both contribute to the final tone we see.
TVI is traditionally used as a metric for maintaining process control as its variance is measured at different stages of the production cycle.
Because it is affected by many variables, TVI should not really be used as a target (I.e. we're trying to get a TVI of 18%). Instead, if the target is to achieve a certain desired print characteristic (e.g. when building tone reproduction curves that are applied to plate output) it is more useful to think in terms of final tones. This means that you don't care what the dot gains are - you just, for example, want to achieve 68% on the press sheet when you ask for 50% in your file.
Print contrast is used to check the quality of press performance in the three-quarter tones. Because it depends to a large extent on SIDs, and it can be altered with a plate curve, it is not very suitable as a variable for standardization (i.e. it shouldn't be used as a metric to determine what SIDs to run at). It is also one of several indirect ways of measuring the maximum volume of ink you can lay down on your substrate. It can also be used to assess various factors such as printing pressure (squeeze), blankets and packing, dampening, inks and additives.
The target is that more print contrast is always better. It is based on a simple principle. As you increase SID from too low to too high the contrast relationship between a 75% tone and a 100% patch of a color changes. When SIDs are too low there is not much difference between the 75% and 100% patches - they lack contrast. As density increases, the difference between the two patches increases or, put another way, the contrast increases. However, as SIDs continue to increase, the 75% tone will start to fill in and hence contrast will start to go down again.
Below is a graphic of an enlarged view of this 75%/100% relationship as you go from not enough SID/low contrast to Optimum SID/contrast to Too high SID/low contrast again:
hope this helps, best, gordo
my print blog here:
Quality In Print