A

Anonymous

Question

Is it possible to change GCR/UCR in a third party ICC profile?

Forum|Forum|4 years ago
September 4, 2021
8 replies
4333 views

Hi everyone. I installed the ICC profile of Blurb printer service. I'd like to change GCR/UCR in order to reduce the ink percentage. Problem is that going to Color Setting > Custom CMYK > Ink Colors... Blurb is absent. It seems I can modify only pre-installed profiles (like SWOP), but not third party ICC profiles.

Is it possible to do in Photoshop? Or do I need another software?

Thanks in advance.

Cross-app workflows

This topic has been closed for replies.

A

Anonymous

Thanks a lot NB (and rob day and thedigitaldog and Stephen and all the other guys) for the nice help. I appreciated su much!
Yes, I'll print a test-copy without re-touching CMYK, then I'll see.

Thanks again.

NB, colourmanagement

Community Expert

Hi

I say follow their instructions and do a test, if it comes back looking disappointing [compared to a proof or properly calibrated display screen] THEN start trying other options.

Your original question

- it's pretty straightforward to rebuild an ICC profile to adjust GCR/UCR and TAC - but you'd need

1: a software that can extract the "training data" [the printed target values] from their ICC profile [or calculate it]

AND

2: a decent ICC print profiling software to make the new profile.

PLUS

3: sufficient knowledge of the output device to ascertain ideal GCR TAC etc.

That normally involves printing test ramps and a TAC target.

It is quite complex to craft a well optimised CMYK profile.

You'd hope Blurb are getting OK results based on their advice, or how do they stay in business?

I hope this helps
neil barstow, colourmanagement net :: adobe forum volunteer
google me "neil barstow colourmanagement" for lots of free articles on colour management
[please only use the blue reply button at the top of the page, this maintains the original thread title and chronological order of posts]

L

Lumigraphics

Legend

Really, only three questions matter here.

1. How does an actual printed page look?

2. Are their press runs consistent, so you can coiunt on repeatable results?

3. Are you willing to change printers if #1 or #2 is unsatisfactory?

If a printed sample looks good and they can hit that target in subsequent press runs, its all good.

Since their process is a black box and they don't seem able to help you make adjustments, if #1 is crap or different press runs look different then you can live with it or find a new printer.

TheDigitalDog

Inspiring

Guys, keep in mind that what Blurb does on their end is a black box!

You can convert using their recommended profile, there's zero guarantee they don't use a Device Link or something similar on the front end to convert to another flavor of CMYK. No one but Blurb knows and they are not telling anyone.

This can all be an expensive experiment.

Best to find a book printer that actually tells users the process down to how and where CMYK gets to the Indigo (and the book covers at Blurb use a different digital press to boot).

Author “Color Management for Photographers" & "Photoshop CC Color Management/pluralsight"

rob day

Community Expert

Right that’s a problem with any automated online printing where the only communication is a FAQ list.

Online printers don’t usually let PDF CMYK output values thru to the press, and if they do you’ll never know when the policy might change. In a fully automated system profiled RGB with Proof Colors turned on would be safer assuming they honor the embedded source profile.

Stephen Marsh

Community Expert

You can find an ink limited GCR version of the target profile here:

https://www.colormanagement.org/en/gracolprofile.html

A

Anonymous

Dear gentlemen, thanks you SO much for your patient replies. Fantastic amount of infos.

You can find an ink limited GCR version of the target profile here:
By @Stephen Marsh

So, I convert my RGB images with GRACoL2006_Coated1_GCR_bas (instead of the regular Blurb_profile). And done? (It sounds to me like a solution, right?...)

Stephen Marsh

Community Expert

Yes, if the Blurb profile is targeting GRACoL2006, but with too much total ink, then the suggested profile will have a lower total ink limit (and also use stronger GCR in neutrals and colours). You can always assign the Blurb profile if you think that embedding a "different but same" profile may introduce an unwanted (by you) colour conversion at the publisher.

Stephen Marsh

Community Expert

Also here:

https://community.adobe.com/t5/photoshop-ecosystem-discussions/tic-grading-reducing-in-cmyk-optimizing-for-k/td-p/12363148

A

Anonymous

Hi everyone, newbie here.

Q: Which workflow to reduce the Total-Ink-Coverage in CMYK optimizing the colour for K?

Let me elaborate:

Let start with a 16 bit RGB image that I want to prepare for printing. After grading, I convert it in CMYK using the printer profile provided by the printer shop, that in this case is Blurb. Blurb's profile goes to 339% of TIC, BUT... they recommend to keep large areas under 300% to avoid overload spots. That means I have to manually correct the amount of ink trying to preserve the colour perception as possible.
How to do that?

My “dirty solution” is to work with Curve in CMYK: if the image has large dark areas with TIC well over 300%, I use CMYK-Curve, reducing CMY only at about 85/87% linearly, then fixing a point around 60-horizontal on each line, then dragging that point (in each curve) toward about 58-vertical. (In short, each curve will be linear up to 60%, and then will start to curve up to the end.) Over this layer, I overlap a copy of the original layer and apply Blend-If at around “7 / 50 - 255”. In this way, I'm sure that only dark areas of the image will be ink-reduced.

Now... As I said, this is a “dirty solution”. The fact is that the automatic conversion from RGB to CMYK (based on the printer profile) is not optimized for K, i.e. PS tries to convert the RGB colours in the most precise way, without caring about ink saving! This implies that a neutral medium grey (RGB 128-128-128) will be converted to CMYK 51-43-43-7 (example in SWOP v2) that is almost identical to 0-1-2-60, where first TIC is 144, whilst second TIC si only 63 (i.e. manually optimized).

My problem is that even with the Curve-method I described above, my colurs will be NOT optimized (I can't really isolate each colour to manually find its optimized version...)
So my question is: is there a finest method to do that?

Really thanks in advance.

A

Anonymous

P.S. I think I could easily solve my problem changing the GCR level of the ICC profile. I can easily customize GCR level of any pre-installed ICC profile directly in Photoshop. But I can't modify Blurb's profile! (Color Setting > Custom CMYK > Ink Colors... but Blurb is absent.)

TheDigitalDog

Inspiring

I replied in the LR forum where you also asked so check there.

The Blurb ICC profile is definitely GRACoL2006 Coated1, right down to the paper white L*a*b*. What they're using is essentially a copy of the IDEAlliance GRACoL profile and has little to do with how they're actually printing.

I have measured all the papers Blurb provides, and just the papers alone are not even close to GRACol 2006. In fact, the deltaE differences in just the two most different papers are nearly dE4!

Again, what you uploade to Blurb through LR (since you asked there) is sRGB. They control the conversions at this point and they don't tell you anything about their actual print process. So the answer is short: no.

Unless you could get a CMYK target printed without color management through Blurb and had the recipe for GCR/UCR, total black etc, AND you used such a custom profile resulting from that AND they honored that CMYK (again impossible though LR), the answer is really a big fat no.

Author “Color Management for Photographers" & "Photoshop CC Color Management/pluralsight"

Derek Cross

Community Expert

I suggest you don't mess with Blurb's settings. Have you had something printed by Blurb and been unhappy with the result, if so the problem may be at your end, for example is your monitor calibrated?

Is there someone at Blurb you can speak to about he issue?

A

Anonymous

@540812
Well, Blurb ICC profile is used for all their types of papers. Clearly it can't be optimized for every product. In fact Blurb custom service wrote to me saying that 339% of TIC is good for details, but if your image has a large dark area, they recommend not to exceed 300% of ink (that for Magazine Premium). Since I have many dark images with large dark areas, I'd prefer to change the GCR of their profile (if possible). But I don't know how! Is there some app that can do that easily?

@705730
Thanks of rthe screenshot. It's simmilar to my Color Settings, but I have “Gray: Dot Gain 20%”. Not Blurb_ICC_Profile.icc
Should I change that parameter?

Really thanks both of you gentlemen!

D Fosse

Community Expert

but I have “Gray: Dot Gain 20%”. Not Blurb_ICC_Profile.icc
Should I change that parameter?

By @10846897

If you have grayscale images, that's the way to do it. Grayscale will go directly to the black plate in whatever CMYK process is used. If you have working gray set up like this, you can select it from all the rolldowns, and if you have files with a different grayscale profile, you should convert to this.

The dot gain profiles are generic and basically outdated.

rob day

Community Expert

Problem is that going to Color Setting > Custom CMYK > Ink Colors... Blurb is absent.

The Photoshop Custom CMYK dialog creates legacy curved based profiles, so while you can set a total ink limit, the resulting profile would not be correct for the Blurb press

Blurb’s CM page states that their press profile Blurb_ICC_Profile.icc is based on GRACol 2006. It has a total ink limit of 337%, so there shouldn’t be a reason to lower the total ink, just use their profile. It should show up in the CMYK Working Space drop down if you installed it correctly.

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