Finger printing

[beanz]

I am planning to do a press fingerprint. i plan to use standard densities for my process colors, to be measured using m0 illuminant of exact,

wet densities:

k=1.9
c=1.5
m=1.5
y=1.0


my questions is what should be my tolerance in density values across the sheet to say that the sheet is an acceptable sample? is it (for example, +-.05 density units difference, etc.)

 

[gordo]

I am planning to do a press fingerprint. i plan to use standard densities for my process colors, to be measured using m0 illuminant of exact,

wet densities:

k=1.9
c=1.5
m=1.5
y=1.0


my questions is what should be my tolerance in density values across the sheet to say that the sheet is an acceptable sample? is it (for example, +-.05 density units difference, etc.)

Those aren't "standard densities. These are (dry measurements - average dryback is 0.05 (yours may differ) so you should be 0.05 points higher than these numbers if measuring wet:

K 1.70
C 1.40
M 1.50
Y 1.05

Instruments vary - make sure that yours has been factory calibrated recently.

+/- 0.05 is a standard tolerance. Remember that solid ink density is an indirect measure of ink film thickness (the control that the press operator has) not a measure of color. During fingerprinting you don't just measure SIDs across the width of the sheet but also lead edge to tail.

Have you selected a test form? The best do not have any reference subjective images.

Do you have a USB microscope?
Ones like this (20x-200x):

Are less than $100 (e.g. on eBay) and are ideal for viewing and recording halftone dot integrity.

Do you have an action plan for conducting the fingerprinting session?

There's much more to it but that's a start.

 

[ColorGeek]

Keep in mind that density has not been part of any printing specification or standard in nearly 10 years. For instance, GRACoL gives you target LAB values for your solid inks (CMYK), plus your overprints (RGB) and CMY grey balance. Any mention of SID's is merely a recommendation. Using the G7 method you print the P2P chart, measure that with a spectrophotometer, and dump the measurements in Curve software (or the like, there are several software programs fro generating curve values). I also use a product called SpotOn that helps me determine exactly what the optimal densities are to achieve the best color match - this way I can tell the press operator exactly what he should be targeting, if he is going to continue to use a densitometer for make-ready.

 

[gordo]

Keep in mind that density has not been part of any printing specification or standard in nearly 10 years. For instance, GRACoL gives you target LAB values for your solid inks (CMYK), plus your overprints (RGB) and CMY grey balance. Any mention of SID's is merely a recommendation.

Correct - but that does not make it right - or best practices, or the complete method, especially for fingerprinting a press.
You can get into a world of pain if you do not understand press mechanics and approach it as if it was a scanner or camera - just looking at LAB values and instructing a press operator as to what to do to bring the press into alignment to those LAB values.

But the OP seems not to be interested in the topic so it is a moot point.