steven kornreich wrote:
I know this has been discussed before, but when determining
ink limits per color and then doing a overall ink limit, reading patches in LAB
for cyan and magenta you look at the L value until it reaches the lowest value
then it settles there or max density. But I am not sure what to look for with
yellow and black, and then when doing a overall ink limit for all four colors
what to look for.
Thanks
Steven,
Without being Rip Specific (you did not mention one), of the
methods I have worked with, I find that the best is a combination of a set of
visual test and a test to be measured with an instrument.
The instrument can tell at which point you reach max
density, which is important, but the results of the measurement test should be
weighted against a set of visual test. The visual test will let you see when
and where you will start to loose detail in your prints.
An example would be boxes with different percentages of
Total Ink (equal parts of the primaries is one way) with reversed out text on
top in 2pt, 4pt, 6pt, etc. Varying percentages from 200-400%. In some cases,
going a little lower my be necessary
Another is just much smaller squares of the same equal parts
of the primaries to just check for bleeding and such,
And my favorite is a red rectangle with circles, instead of
squares of those same primaries aligned across the red rectangle. Inside of the
black circles, place a smaller circle with a white outline and no fill. For
this test you would look to see at which point the black circle starts to bleed
into the red background and at which point the white circle starts to fill-in
(losing detail), from the black circle starting to bleed into it.
There will be times where detail (I think I remember you
also do Fine Art Printing) will be more important than max density, and vise
versa.
With the measurements obtained from a spectro, in
combination with some of these visual tests, you will be better equipped to
determine ‘which’ limit is best for your application at hand.
As to yellow, as well as the other primaries, if you read
the color spectrally, using the calculated Chroma value should give you a truer
read. If you don’t have anything to do the conversion from the spectral
data, Bruce Lindbloom has some wonderful spectral calculators on his site.
If you have a measurement file you are currently working on,
if you contact me off list I will turn it into a spreadsheet for you.
Using that L* value on Yellow has screwed me on more than
one occasion.
Cedric Briscoe
Treetop Publishing, Inc.