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

[Guest]

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.

[Guest]

As I mentioned earlier, you can first convert the lowkey images using the GCR BAS profile, THEN assign the Blurb profile...

By @Stephen_A_Marsh

I tried: I converted a lowkey image using GCR BAS profile (result is fine), then I assign Blurb profile. The result is that image maintains the same CMYK values of GCR BAS, but is visually washed-out 😞

[rob day]

then I assign Blurb profile. The result is that image maintains the same CMYK values of GCR BAS, but is visually washed-out 😞

I’m not seeing that, can you show a screen capture of the difference? Do you have Proof Colors turned off? You don’t need Proof Colors when you are viewing in the output space.

Just to be clear I agree with @TheDigitalDog, it’s unlikely your final PDF’s CMYK values will be output—you would have to run a test print and check the press sheet values to know for sure.

[Guest]

Unfortunately remaining time doesn't allow a test print...

Here 2 screenshots:

1st is BLURB ICC (no Proof Colors)

2nd is GRACOL-assign-Blurb (no Proof Colors)

To me, converting to Gracol and then assigning to Blurb ICC doesn't work: 2nd image is a bit “washed” in comparison with the first.
IMO the reson is that Blurb ICC “reads” 300% NOT as his TIC, so not as his dark shadow. Gracol does it, but if final profile is Blurb ICC, then it will read Gracol's TIC as a lighten shadow.

Guys... please give me an advice about this: if you have low-key photos, with big shadow areas between 314-337% of Blurb ICC, would you leave the CMYK conversion as it come from Blurb ICC conversion? (Would you trust in Blurb's 337% TIC?) Or instead you'd try to do some adjustment Curves in CMYK to reduce the amount of ink?
Anyone of you have experience of low-key photos converted with Blurb ICC CMYK? If so, which is the printed result?

Really thanks.

[TheDigitalDog]

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@Deleted User wrote:

Guys... please give me an advice about this: if you have low-key photos, with big shadow areas between 314-337% of Blurb ICC, would you leave the CMYK conversion as it come from Blurb ICC conversion? 

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I guess my 'advise' wasn't strong enough as stated in the several forums this was asked: Don't go there! You have zero idea what you provide with any non standard/advised Blurb process will produce, you can't run a test, this is an expensive route to take. Send them tagged RGB out of LR if wish, send them CMYK exactly as they demand. Anything else is likely to result in unexpected and poor results. 

[rob day]

you can't run a test, this is an expensive route to take

Looks like you can press proof a single copy of a 20 pg 7x7 soft cover for $20.

I always run targets with online printers to find out how they handle PDF/X DeviceCMYK. A black only 0|0|0|0 to 0|0|0|100 ramp would convert to 4-color with a regular CMYK to CMYK conversion. Device link conversions are harder to spot, but a built CMY swatch, something like 50|50|50|0, would likely get black added on a device link conversion.

But still there’s no way to communicate, so you never can be sure when they’ll change output conversions.

[rob day]

Hi @Deleted User , I’m not sure why you care about the ink limit—the point of total ink limits is to prevent ink offset, not produce more accurate color. If Blurb can’t handle the GRACol 337% limit it’s their problem—in that case they shouldn’t be providing the profile.

Also, the conversion to CMYK can happen anywhere in the workflow—it could be up front in Photoshop, on export to PDF, or at output at Blurb. Assuming the destination profile and intent are the same for all 3, the results would be the same.

You could make the conversion to Blurb’s CMYK followed by a CMYK color correction, but you would have the same problem—Blurb might not be allowing the corrected CMYK numbers to be output unchanged.

[Guest]

I’m not sure why you care about the ink limit...

By @rob day

Well, the “nonsense” point is that Blurb itself offers a conversion profile that converts images up to 337% in the darks, but at the same time they recommend that most of your image doesn't exceed 300% to avoid print blots. A nice puzzle for a low-key magazine! (IMO they have in mind only outdoor sunny-day photos...)
The other nice “nonsense” is that Blurb says you can use their inky-fat profile, OR... the good old SWOP v2 coated (...what the hell happens when the project hits their printers?...)

The SWOP option is unsettling because confirm their attitude for the more common 300% limit. At the same time, if you limit Blurb_ICC's TIC near to 300% (using Curves), the result is a bit “washed out”. 

My goal is finding someone that says: «I had low-key photos, I converted them in Blurb ICC CMYK, I noticed that most of the image was around 315-337% but I didn't give a damn, and anyway the result was very good!»
...

But until I find someone who says so, I think my workflow could be:

1. Converting RGB to GRACoL_GCR_bas (K optimized and TIC at 300%);

2. Assigning Blurb ICC (that will “wash” the images a bit, because of the empty “room” in the darks between 300-337%);

3. Compensating the empty “room” with a touch of Curves, stretching a bit to recover some darks, just up to 315%.

Let say it's my test 😉

[Abambo]

It's not a good relationship if Blurb says to do so and with the same breath don't do so, but we won't tell you how to do...

Normally, doing the CMYK conversion at the very last moment provides the best results, as long as you do not manage the whole process until the press output. So, the best advice I read here was @rob day  suggesting keeping the pictures in RGB. That's what I would certainly do.

[rob day]

the good old SWOP v2 coated (...what the hell happens when the project hits their printers?...)

Why do you think they are going to let the SWOP CMYK values output? If you export to the default PDF/X-3 with SWOP as your InDesign document assignment, US Web Coated SWOP will be the Output Intent and they will likely make a Device Link, or regular CMYK-to-CMYK conversion, to their actual output profile. Again they are accepting the 337% total ink produced by their provided profile—whether they can print that coverage without offset isn’t your problem.

[TheDigitalDog]

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). 

[rob day]

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.

[NB, colourmanagement net]

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]

[Lumigraphics]

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.

[Guest]

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.