Re: B+W in CMYK

Lee Varis

On Monday, May 6, 2002, at 06:26 AM, Scott Olswold wrote:

The best possible way is to find/make/buy a profile based on the print
provider's device and convert to CMYK using that profile. This way, the ink
limit and black generation should work with their setup *and* you don't have
to play mucky-muck with adjusting this or that.
This is not an option - The magazine is printing using a web press. The fact that they are giving me fairly high dot gain specs suggests that they are aware of relatively poor press performance with regards to dot gain and I will tend to "believe" that they know what they are talking about ( most of the time I get a fairly lame response from a print production person like, "we don't have any dot gain" when I ask them about these things.) I don't have the time to profile their press - they don't use a profiled workflow and the press is probably too variable to get a good profile anyway. I will not have the opportunity to get a matchprint made nor do they have enough control at the print run to adjust for individual pages to match the matchprint - this is going into a consumer grade 'zine with lots of other articles and ads besides mine. - in other words this is the real world!

Now, given how you *are* doing things, what I would do is this:

1. Keep GCR set to Medium and set your TIL and Black to what's specified by
the output house.
Given that I'm separating B+W images with no color in them and that I want these "B+W photos" to look as neutral as possible, wouldn't it be better to use a heavier GCR (more black ink) to avoid possible color cast if the press varies in dot gain on any of the color plates?

2. Convert your image *first* to RGB and then move to CMYK. This will
probably introduce more tone in the CMY channels. This is good, because
we're going to play with Black.
These images are in RGB, though they are completely neutral color wise, I'm separating them to CMYK because I have color and B+W on the same page and I don't want a tepid grayscale (100% black ink only) image displayed next to a full color CMYK file that will have a 280% ink coverage for it's black point. I'm not looking for more "color" tone - I'm looking for less color, more value range

3. Observe the Black channel. You can use Levels or Curves to tone it down
just a punch more in the deeper shadows. Since you have some ink in CMY for
those areas, it won't affect your overall image that much (specifically on
'zine stock, unless your 'zine is "upper shelf" stock like Nat'l Geog.).
I think your understanding of what I need is backwards - I'm NOT looking for maximum color gamut - I'm looking for minimum color gamut and maximum value range. I think I'd like to replace more of the color ink with black - I'm just not sure how far I can go without creating problems for the maximum value range that I'm after.

I'd like to hear from anyone who might have a particular trick for dealing with this specific scenario - separating B+W images as CMYK - I won't be able to do duatones or tritones so don't bother suggesting things that rely on custom duo/tritones. Are there things I can do with UCA in combination with some other settings? Any creative ideas are welcome - I understand the basic principles of CMYK and Photoshop's custom CMYK setup. Thanks in advance!


Lee Varis

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