Depends on the nature of the image. If there is nothing but white behind the black, I use this technique:
Select the black areas, hit copy.
Switch to black channel, hit paste.
Adjust CMY curves from 100% to 0%, adjust K curve ~75% to 100%.
This copies the full range of image information into the black channel and then "bumps up" the black channel so that the K is 100% and not 87% or what have you.
If we’re talking a photograph (in which case I can’t see why you’d want the blacks 100% K), use Select Color Range to select the blacks, adjust your selection edges via feathering or expand/contract, select similar, etc. and apply the curves as above. Be warned the blacks will look washed out compared to the other colors and are likely to have a "halo" effect of CMY black if you under-select or the surrounding color is likely to darken if you over-select.
Are you sure your publisher isn’t referring to typographical elements? What type of piece are your printing – subject matter, press type, paper type, etc. To specify that type of black generation is to not really understand most commonly used printing processes.
You can, of course, use an output profile that has maximum black generation for you conversion that will give you 100 percent black, but you’re still going to have some CMY in the blacks. In fact, you NEED some in the blacks or your transitions into the shadows will be really harsh.
A very reliable workflow is this one:
a) convert RGB (gamma) into to Grayscale (same gamma).
b) convert Grayscale by a custom CMYK profile with
max.black generation into a K-only CMYK file.
This K-only CMYK version contains three empty plates
CMY. This is not a disadvantage (easily observed
by the prepress operater).
If the max.black generation custom profile is derived
from a valid CMYK version (e.g. ISOCoated), then the
tone reproduction curve of this profile is used and
any guess about gamma or dot gain is obsolete.
Of course one needs K-only printing – it’s simply
cheaper than printing B/W by rich black.
Best regards –Gernot Hoffmann
Thanks Tony, I have tried your suggestions with success on first part. Will proceed. Peter, you hit the nail on head in saying that I have inadequate knowledge of print processes. I do graphics for video and have an employee who does the print processes. He took off for another job and left me facing a print deadline. I am trying to learn very quickly. Thanks for you help.
Gernot, thanks. Tried your suggestions on the print part and worked. And you are right of course that it is cheaper. That was mentioned by the printer and he also said he did not want my print to look like the funny papers.
Thanks to you all. Nice to know beginners can get help. Could not find solution on "help" or in other discussions here on CMYK black.
bob
