Colour managing/process controlling process colour tints

[Paul Sherfield]

Hi

What are peoples views on managing process tints in relation to standard printing conditions.

a) Should a 50% cyan tint in ID print as a 50% on paper or

b) Should this 50% tint reflect the printing conditions, say ISO coated v2, curve A and print at 64%?

I am interested in peoples view as I am considering publishing a 'Tint Book' based on ISO 12647/2

Regards

Paul Sherfield

[disbellj]

The answer would be B. Dot gain is in the ICC profile too (because it describes a process that has dot gain), so what you see when looking at 50% in the program actually looks like 65-70% because of dot gain. So just build your tints as what you're used to (50%), set up the press to ISO 12647-2, and the 50% will measure 70% on press sheet and look just like what you see in your program with 50%. You can't and don't want to try and change this. Even if you could get a 50 in file to measure a 50 on paper, you wouldn't want to. It would be way too light.

Don

[meddington]

I would think for a tint book to have any real value it should be based on standard printing conditions, so I'd vote for b.

We printed tint boks here a long while back. Do you feel that tint books are as relevant today given ICC color management and the accuracy of hard/soft profing?

[PeterA]

We printed tint boks here a long while back. Do you feel that tint books are as relevant today given ICC color management and the accuracy of hard/soft profing?

Michael dont you think we are really forgetting the requirement of our global accounts - who just want the colour in their logo to look the same al around the world - I should think they are amazed to think that you are talking about 50 = 70% (which would be +-4% ) so could be up to 74% where as in Europe we print (sheetfed) 50 = 64% + - 4% so could be 60% - Paiuls idea that 50 = 50% sorts that out and would let the profile resolve the different countries requirement for rgb to cmyk conversion. whilst keeping the CMYK tints the same -its a great idea
Peter

[disbellj]

No it's not a great idea. If you want the countries to print the same, then see how close they print now. ISOcoatedv2 and GRACoL2006_Coated1v2 are very close anyways. In fact, if everyone knew how close they were, they probably would ask in large numbers for one unified/universal characterization data and ICC profile.



Note: TVI/Dot Gain obtained by getting Lab values, converting them to XYZ values, and then determining TVI/Dot gain from XYZ values. See Bruce Lindbloom's LabDotGainCalculator and Don Hutcheson's website for his Formulae, which both give the same TVI although using two different formulas for getting the intermediate XYZ values (I have made the calculators to prove it). The IDEAlink Curve software, Bruce Lindbloom, and Don Hutcheson all three use the same formula to get TVI numbers from XYZ. Also, my calculator I built using these formulas has been shown to be within 1% accuracy to PerfX Press Curves software by Louis Dery himself.

GRACoL2006_Coated1v2
K 50 TVI = 19.41, C 50 TVI = 12.95, M 50 TVI = 14.15, Y 50 TVI = 15.57

ISOcoatedv2
K 50 TVI = 16.90, C 50 TVI = 10.42, M 50 TVI = 14.15, Y 50 TVI = 13.67

Difference between the two
K 50 TVI diff = 2.51, C 50 TVI diff = 2.53, M 50 TVI diff = 0, Y 50 TVI diff = 1.91

So they share the same solids, the same paper brightness, and have really close TVI between the two. You can barely see a difference between the two when the same CMYK values are proofed/printed on the two different printing conditions and compared.

As I said before, if you tried to make 50 in file to measure 50 on paper, it would be WAY TOO LIGHT. Please conform to standards and most won't see a difference between the two anyways - even if printing the same CMYK values in the file on both and comparing side-by-side. Proof your CMYK numbers on a calibrated and profiled proofer to both ISOcoatedv2 and GRACoL2006_Coated1v2 (using standard profile as source and custom proofer profile as destination), compare, and see for yourself. Or soft-proof your CMYK numbers on a calibrated and profiled monitor using the standard profiles to proof in Photoshop (check keep numbers, also check simulate paper and ink), and compare to see really how close they are.

Then we can get past this and on to something else (like out-of-gamut colors being mapped into the gamut to get the best reproduction of those out-of-gamut colors, so we don't get purple or different blues when converting the same e.g. RGB Blue to CMYK).

Don

[meddington]

>dont you think we are really forgetting the requirement of our global accounts - who just want the colour in their logo to look the same al around the world >

Al the more reason why ICC color management would lead to a better predictor of appearance than a static, hard copy tint book created with one particular combination of ink/paper/dot shape/screening, not to mention print process.


>Paiuls idea that 50 = 50% sorts that out and would let the profile resolve the different countries requirement for rgb to cmyk conversion. whilst keeping the CMYK tints the same -its a great idea>

I understand where you're coming from , but the 50=50% idea would involve forcing a press into a totally unatural response. Dot gain is a inherent attribute of print. As Don pointed out, ISO and Gracol definitions are not very far apart at all, and allow for a more natural and optimal response from the press. Forcing the tonal response to a linear output would, IMO, likely lead to instability, banding, and require some seriously heavy lifting from both the press curves and ICC profiles involved. Dot gain is natural so why try to mask it? Most presses will require only subtle to moderate adjustments, depending on dot shape/line screen, to optimize toward current standards/specifications, where we would be talking some hard core cutback curves to achieve linear output.

[PeterA]

Michael

I need to do some testing before answering - I run solely stacatto so I I have no idea what I reduce when I move my 50% linear dor to about 32% to = 64% :-)

Peter

[v BONES v]

CMYK is device dependent.

It will always look different under different printing conditions - you _must_ allow for gain!

[seejay]

Hi Paul,

I would err toward B based on personal experience.

We have come across a situation whereby part of a job prints out of process (with relevant spot colour conversions) and the balance of the job printed black and spot. In order for them to match reasonably closely we had to run both elements to ISO.

Very interested in this aspect of ISO12647 as I believe that this is one area that is not receiving much attention.

Seejay.

PS. Thought your presentation at the recent BPIF ISO conference was excellent - it has spurred us along to revisit much of our thoughts on colour throughout the workflow and solved a few upstream problems with clients at the same time.

[michaelejahn]

Well, I would disagree that one must allow for dot gain. There are many printing processes where you have to fight dot LOSS. this has ALWAYS been a stupid term (dot gain = stupid term) as it should have always be tone variance or something like that. Total Tone Variance. Maybe that was what 3M's George Lyda suggested, can't recall.

Move to a color managed workflow and get your press in order - that is the marking orders!

<smile>

I suggest that, as we all KNOW are going to be printing digital in some form. When that job is re-run on a Xerox iGen in Indianapolis and an Kodak Nexpress in Nashville, well, dot gain - or applying dot gain curves - well, this simply has no business in that discussion - which is why (again) to create a reliable digital master PDF, it must have an embedded output intent, and we all need to exchange PDF files that follow a standard.