Conflicting Lab Color Values

[Rudstar]

We are screen printers, and I am trying to set some print standards for our printers. ISO 12647-5

Fogra9 is for screen print, but i can't seem to find a profile to install (SC_GC2_CO_F30), only find the data.
However, Fogra information sheet says Fogra9 is practically identical to offset on gloss art paper (Fogra39?),
so should i forget about Fogra9 and use fogra39?

For Fogra9, why are the Lab values different (Fogra Vs. ISO) when they are both for 12647-5, gamut class 2, especially in Cyan and Yellow? Both are black backing for measurements.

Fogra9s.txt (Screen printing acc. ISO 12642-5, SC_GC2_CO_F30, gamut class 2)
Lab Values
100 Cyan 57.36 -37.40 -49.83
100 Magenta 47.68 73.16 -6.13
100 Yellow 88.28 -4.97 94.76
100 Black 19.14 -0.14 1.44

ISO 12647-5 (gamut class 2)
Lab Values
100 Cyan 52 -33 -51
100 Magenta 47 74 -5
100 Yellow 89 -9 83
100 Black 18 0 0

Once i know which Lab values to aim for, then i'll continue on with a test print on the press to do some measurements of solids and halftones etc..
(At the moment we print by eye, but we will get a densitometer soon to measure halftones properly so we can create better (correct) films and prints etc. with a standard to aim for)

Thanks for your help!
Brett

 

[Stephen Marsh]

Looking at the resources, I too can't find any ICC:

FOGRA characterization data
FOGRA9
http://www.color.org/FOGRA9S.txt
Characterization data for standardized printing conditions - www.fogra.org
Download von Charakterisierungsdaten - www.fogra.org

Do you know what the total CMYK ink limit is for your screen printing?


Stephen Marsh

 

[Rudstar]

Hi Stephen,
Do you know what the total CMYK ink limit is for your screen printing?
No we don't have any ink limits at the moment. I just output our separation films without any of these types of adjustments at the moment.

ISO 12647-5 states the following, so i would probably then look towards ink limit values from 12647-2 if needed.

4.2.6 Tone value sum
There is no restriction on the tone value sum.
NOTE Tone value sums between 300 % and 400 % may be used. However, in order to match products from other
processes, a lower tone value sum may be appropriate.

Brett

 

[Stephen Marsh]

Brett,

You mention the need to get hardware - a densitometer. You may also need a spectrophotometer, or perhaps a combined spectrodensitometer.

Without knowing how the measurements compared, I was skeptical that you may be able to "get away with" using F39 for your F9 printing conditions, however after making an ICC profile from two separate ICC packages from the same characterisation data, the F9 is indeed very close to the F39 in gamut shape and size when compared to good profiles such as below:

colormanagement - ISO Profile F39 300%
colormanagement - ISO Profile F39 300% GCR

That being said, grey balance is just a little different between F9 and F39. It probably depends on how close your screen printing is to F9 or F39 on which condition will suit you best if you are going to separate to and/or print to a specification.


Stephen Marsh

 

[Rudstar]

So maybe I use ISO Coated v2 (or Fogra39 coated), but then aim to relevant screen print specs in 12647-5?
(Ah, this gets confusing sometimes!)

We will get a densitometer and/or spectrophotometer soon for press and proofing etc. so i know we are hitting our targets.

Brett