For many photographers, CMYK printing is an unfamiliar process, and fortunately they rarely need to deal with it. However, if you wish to advertise your services in the local newspaper, you will likely need to supply a CMYK file. Here’s a few pointers to help the process go smoothly.
- This article only applies to advertising, where CMYK files are specifically requested. It does not pertain to editorial photographs, which should be supplied as sRGB files.
- This article applies to all versions of Photoshop, but not Photoshop Elements.
- This article assumes some knowledge of standard post-processing techniques, and colour-management principles.
Introduction: Asking the right questions
Upon enquiry, you’ll be given the publisher’s Material Specifications. These will tell you the required size and resolution, and deadlines, and stuff, but their colour specs are often woefully inadequate. All you’ll get is "Files must be CMYK", without a shred of further information.
If so, you need to contact them to ask for an accurate ICC profile. Don’t ask the sales rep, they won’t have a clue – try to speak to the Prepress department.
A modern metropolitan newspaper is likely to be able to supply you with a CMYK profile for their printing press. If so, that’s fabulous – download it and proceed straight down to Part Two of this article.
However, a suburban or regional newspaper might not be so well-managed. If the only answer you get is "Um … what?", or a parrot-like repetition of "Files must be CMYK", then you’ll need to read Part One of this article.
Part One: Preparing a profile
So you’re on the phone, and your request for an ICC profile has come to naught. You need to gather a couple of important bits of information to give yourself a fighting chance at satisfactory printing.
- Question 1: What is the Dot Gain on your press?
- Question 2: What is the Total Ink Limit required?
These questions are critical. Refuse to hang up the phone until you’ve talked to someone who can give you precise answers. As a general guide, newspaper Dot Gain is somewhere between 20-30%, and the Total Ink Limit is 220-270%.
Write down the figures, because now we’re going to make our own ICC profile.
Please note: All hope of a perfect screen-to-press match is now gone. Sorry, but it is. Our strategy from here is simply to produce a result that’s “in the ballpark”, and won’t make you ill when you see it in the paper tomorrow.
1. Open Photoshop.
(I wrote this article when I had CS2, but it works for all versions of Photoshop.)
2. Open the Color Settings.
Edit>Color Settings, or Ctrl-Shift-K.
3. Custom CMYK.
In the "Working spaces" section, select "Custom CMYK" in the CMYK drop-down menu.
4. SWOP (Newsprint).
Choose "SWOP (Newsprint)" in the "Ink Colors" drop-down menu.
5. Dot Gain.
Enter the Dot Gain figure you’ve been given.
Leave the "Separation Type" as GCR, unless you’ve been specifically told otherwise.
7. Black Graph.
Choose "Custom" from the "Black Generation" menu, then adjust the curve as shown below.
8. TIL and UCA.
Enter the Total Ink Limit figure you’ve been given. For good measure, add 30% of UCA (although I’m unconvinced it does much!)
9. Name the profile.
Call it "Newsprint" or whatever, then press "Ok".
10. Save the profile.
Drop down the "CMYK" menu again, and choose "Save CMYK". Photoshop should automatically point to the correct folder, so just press "Save". Your newsprint ICC profile (crude though it is) is ready to use.
11. Get out of there.
Cancel out of Color Settings. You don’t need to keep the newsprint setting active.
Part Two: CMYK gamut
Now you’ve got a CMYK ICC profile (one way or another), you can prepare your CMYK file.
Depending on the nature of your advert, you might choose to build a CMYK file from the beginning; or you might prepare the whole thing in RGB, and convert at the end. This article doesn’t discuss all of that.
All I want to focus on is the matter of out-of-gamut colours.
Newsprint has a tiny gamut. An eensy weensy gamut, in fact. Wander past a newsagency, and take a look at the brightest red in a newspaper, compared to the bightest red in a magazine. Dull, huh?
So, when you convert RGB to newsprint CMYK, you might get a shock. Some of your bright colours will die. It’s disappointing, but we just have to make the best of it.
Photoshop gives us a few ways of checking for these out-of-gamut colours before conversion:
Soft-proof using the Newsprint ICC profile to see which colours "ain’t gonna make it".
(More information about soft-proofing here.)
2. Gamut warning.
After soft-proofing, turn on the gamut warning to see the bad news more clearly.
3. Info panel.
As you run your mouse pointer over out-of-gamut areas, you’ll see your Info Palette will display an exclamation mark ("!") after the CMYK values.
Part Three: Prepare and convert to CMYK
If you identify any out-of-gamut areas, you’ll need to desaturate those colours. (I’ve seen photographers optimistically trying to saturate o-o-g colours in the vain hope that it will somehow get better … it doesn’t. If a bucket is full, pouring more water into it won’t help – it’ll just make your floor messier.)
So use Hue/Saturation as necessary to reduce the gamut of your brightest colours. As you move the slider, check your Gamut Warning or Info Palette to see when to stop.
The resultant image will be a duller version of itself, but there won’t be any nasty surprises when you convert.
After that, it’s straightforward. Use "Convert to profile" in the Edit menu to convert your RGB file to newsprint CMYK.
Send it off, cross your fingers, and remind yourself that nobody else who reads the paper tomorrow will examine the colour in your ad as closely as you.
Like to know more?
If you prepare a lot of material for press printing, you'll love my Prepress Class. You'll learn about CMYK, gamut, and soft-proofing in great depth. It's very affordable and very empowering.
If you have a question about this article, please feel free to post it in Ask Damien.