Both GCR and UCR are techniques for substituting a certain (correct) mix of black in from CMY. That is, with UCR, if there’s a neutral or near neutral made up of a specific mix of CMY inks, those are replaced with black ink. This saves money since CMY inks are more expensive than black ink, helps reduce the amount of ink used, can assist in producing better blacks on presss and neutrals etc. GCR does pretty much the same process but isn’t limited to just neutrals. It can replace CMY with black ink in other areas of an image. Gray Component Replacement (GCR) gives you an idea what’s going on here.
If you have a profile building application, you are usually asked which you want and with GCR, you have a number of options (none, light, medium, heavy etc). This can also be done in Photoshop’s classic CMYK engine but I’m not comfortable recommending users go that route (it’s flakey). But you can at least get an idea of what this all does. Go into the color settings/CMYK working space and toggle to Custom. You’ll see a dialog where you can play with different settings. Watch the curves! You’ll see as you set different GCR settings how black is replacing CMY inks.
Oh, UCR is used more often for newspaper while GCR is a better option for higher quality printing (pressman usually prefer UCR, it gives them more options on press but GCR is far more useful).
This saves money since CMY inks are more expensive than black ink, helps reduce the amount of ink used, can assist in producing better blacks on press and neutrals etc
Actually it helps the pressman hide bad separations and gives more flexibility in hitting a more neutral 4 color black.
and helps press slur, dot fit, dot trap, etc.
bottom line, press, (JOB) control.
Is there a way to create a custom profile like for newsprint using the color settings CMYK menu and still be able to use Adobe’s current award winning color engine and not have it revert to the classic used in PS 4 & 5 when doing an RGB to CMYK conversion?
Well,
for a single color black press run, you really don’t need all the spectral info that a 4 color profile generates. So, you can use the old color look up tables, "in manual mode" to build a press curve that describes the plate setter and press gain, but just profile the damn thing and take the guess work out of it.
Since there is considerable variance in difference newsprint presses, it’s often useful to talk to the prepress departments at the respective publications. Newsprint prepress guys, unlike sheetfed are much more likely to have settings that work for their press, as they have had to figure out how to keep their advertiser coming back. None of the canned newsprint profiles I used to have were worth much, as no two presses were that close to one another. A custom profile would be great if, and it’s a big if, they’ll let you run a target and make a profile. The classic PS engine can work just fine if it has the right ink values and dot gain information plugged into it. It might be easier to get a printer to run a strip of the the nine printing inks colors than to have them set aside the room for a complete profile target.
–>the classic PS engine can work just fine if it has the right ink values and dot gain information plugged into it.
It does some funky stuff. Do this, go in and ask for 300 total ink, convert an RGB file with 0/0/0 to CMYK and tell me what total ink reading you see in the info palette.
Then go in and change Black limit lower than 100%. You’d think that would affect total ink. It does but in a very strange way.
I think best to stay away from this classic engine if there’s any possibility you can actually work with a CMYK ICC profile. When you convert 0/0/0 using SWOP Coated v2, you get the correct 300% total ink reading you don’t get with the SWOP setting in Classic. I’m at odds to figure this one out.
That’s what I was talking about. Thanks, Andrew.
I touched upon this subject in the Color Management forum and others confirmed the same.
I tried to alter visually only the inksets of the default SWOP and Sheetfed Adobe profiles just to see what kind of preview I would get in a conversion with the newly created custom CMYK profile. I get a preview similar to PS 4 & 5 SWOP profile.
Just curious… I’d been led to believe some years ago that newspapers did not use standard cmyk separations for images. Black is retained for text only, and all photo images are separated as cmy only. If this is true, wouldn’t UCR and GCR be counter-productive in a newspaper environment? My information may be old, or may have been inaccurate. (I don’t recall where I learned it, but at the time I checked some newspaper photos under a lupe and I was convinced.) Anyone who works for newspaper prepress out there who could confirm or deny this?
Andrew,
That’s only if you are using Medium Black or above. Choose Light Black Generation and it works as expected. Change the Black limit to 90% and the total ink does drop a few ticks, but that’s easily solved by raising the total ink up to 305. That’s something you often have to do with a custom ICC profile anyhow to get the exact ink level you want. If you plug in custom ink measurements, the results can be quite good. I’m not saying that it’s better than a full fledged ICC profile, just that it can be a very workable solution, if nothing better is available.
