Black to Rich Black in Photoshop

Rich black applies to graphic elements designed directly in CMYK, using all four plates, as opposed to K-only black.

In a photograph or any RGB image, this handled by the profiles. You always get rich black. 0-0-0 in RGB will map to whatever the profile defines as maximum ink. This ink limit, known as Total Area Coverage (TAC) is built into any CMYK profile. If you exceed this limit, you may get drying problems and ink smearing.

4-color offset print usually has a pretty high black point. There are two components to this - one is this ink limit; the other is paper reflectance. The profile accounts for the first but not the second.

In any case, you need to plan for this. The way I do it, and which I think is the most efficient and accurate way, is to calibrate the monitor's black point to be a visual match to a finished print. In practical numbers, this often means a black point around 1.0 - 1.5 cd/m². This is way higher than most monitors' native black at 0.1 - 0.2 cd/m² - but you won't be disappointed when you see the result.

Hi, that’s not a dumb question at all. So, the printers instructed you to softproof using a GRACoL profile [there are a few variants, you'd need to use the actual right one, can you please tell which specific GRACoL profile that was?]?

Are you sending them RGB or converting to the GRACoL profile they gave you? If you send RGB then you have no control over this.

IF tyoumare converting tomthe GRACoL?? icc profile you can look at the values using Photoshops eyedropper / info pallete.

Some people print a black and white image (often as as a greyscale file) using black ink only, that means blacks may be a little weak.

"Rich black" generally means printing a black and white image using the full set of CMYK inks. 

Perhaps that's what you did [converted to GRACoL xxx?] and you got a greyish (not black result)?
We need more info really.

Converting a monochrome RGB file to GRACoLxx? will inevitably mean that blacks are underlaid with coloured ink. Is that a rich black? depends how that GRACoLxx? icc profile that was used was made.

We can look at the GRACoL ICC once you tell us which one it was.

You could use a custom made "rich black" CMYK ICC profile which would need to otherwise comply with the parameters of the GRACoL profile of course, inklimits, greybalance etc. So, it would be made from the same European characterisation data GRACoL uses - I'd imagine, with the black (GCR) curve set reasonably high. Someone who understands CMYK profile making can do that for you.

On opress the more colour there is beneath blacks, the more likely it is that the greybalance might shift away from neutral. 

There MAY be a way to make a CMYK file and edit it to make rich black version lets hope someone chips in on that.

here's a bit about "Rich Black"

more here

and here 

the latter (manually edit) looks risky to me, because messing with CMY values can skew the printed greyblance.

I hope this helps
neil barstow, colourmanagement net :: adobe forum volunteer
google me "neil barstow colourmanagement" for lots of free articles on colour management
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