One of the concerns in commercial printing is to make sure not too much ink (or toner) is applied to the paper. With the CMYK color print model, inks in four colors are combined in various proportions to create all other colors. It’s possible for a document to call for up to 100% coverage for each ink, for a total of 400% coverage. Think of four solid layers of ink rapidly being laid on top of each other, and I think you can imagine this might cause a problem.
How much coverage is OK will vary according to the ink and the paper. Offset printing on typical book paper can go up to 300% coverage with no trouble. Offset on newsprint, which is more absorbent, can safely go up to only 240%. And 240% is also a figure often cited for printing of book covers on POD presses. This might in some cases be due to the paper used, but it’s even more commonly because of the cover’s plastic laminate. POD book covers are today printed mostly on HP Indigo presses, which are inkjets using special oil-based ink. Put too much of it on the cover, and you can have trouble with laminate not sticking.
Though Lightning Source has long recommended this 240% total ink limit on covers, it is only since 2009 that it has enforced it by rejecting files that significantly exceed it. Such rejections catch many less tech-savvy publishers off guard, and even experienced book designers may not know a good way to deal with this.
So, how do you make sure your book cover is compliant? The simplest approach is to avoid big blocks of dark color in your background and images. (Small areas of it are OK.) In fact, this is probably the only way you can deal with it if you’re using consumer-level programs to design your covers and generate PDF files. Such programs typically do not support CMYK at all, so you have no way to measure or adjust ink coverage directly.
You have much more capability if you’re working with professional programs like Adobe’s Photoshop (not Photoshop Elements), InDesign, and Acrobat Pro. To start with, you can check your cover design reliably before you submit it to Lightning. In Photoshop, you can check total ink coverage at specific points with the Info panel. In Acrobat Pro, you can check the entire cover in one step with Output Preview or with a customized Preflight profile. And of course, in either Photoshop or InDesign, some colors can be defined by you directly. (If you’re not sure how to handle any of these tasks, please see the program documentation.)
Areas of single color defined manually or automatically are easy enough to change. For instance, the black that Adobe’s programs normally use for type is a “rich black” with 300% coverage. For display type, you can instead create and apply a swatch with Lightning’s recommended 60% C, 40% M, 40% Y, and 100% K. For regular text, you should apply “pure black” of just 100% K.
But what if darker colors are all mixed into a continuous-tone graphic like a photo or a scanned painting? Lightning has issued a recommended procedure for handling this in Photoshop. Unfortunately, as the instructions delicately put it, “there will be visible color changes.” This is because the procedure is based on a legacy feature from Photoshop 2—not CS2, but just 2! Really, what’s needed is for Lightning to develop a dedicated color profile to manage conversion—but Lightning remains committed to discouraging color management entirely. In fact, the whole problem arises because Lightning expects us to prepare files to a print standard—U.S. Web Coated (SWOP) v2—that is built around coverages up to 300%!
With some experimenting, I’ve modified Lightning’s technique and settings so images that need fixing should stay close to their original colors—at least close enough to require minimal adjustment.
Before we go over these, though, let me stress that this is not something you should do unless you must. Inevitably, your image will to some extent be degraded. Also keep in mind that Lightning is not super-strict about the ink limit. Isolated areas over the limit will probably be accepted. So, unless you have a photo of a coal miner at work in the mine at midnight with his lamp turned off and a black cat curled around his leg, you might not need to worry at all. If in doubt, the best strategy is to submit your cover as is and see whether Lightning accepts it.
OK, here are the steps. Again, this is for adjustment of continuous-tone images in Photoshop. (I’m using Photoshop CS4.)
1. Open your image in Photoshop. If you have any other adjustments to make to your color space—such as I recommend in my article “Better Color from Print on Demand”—do them now. Otherwise, it’s best to start with your graphic in an RGB version rather than in one already converted to CMYK.
2. Go to Edit > Convert to Profile, or in older versions, to Image > Mode > Convert to Profile. Under Conversion Options, use these settings:
Engine: Adobe (ACE)
Intent: Relative Colorimetric
Use Black Point Compensation: Yes
Use Dither: Yes
3. For the destination space profile, choose “Custom CMYK.” If you get a warning about color management, click “OK.” Then, in the new dialog box, enter these settings.
Ink Colors: SWOP (Newsprint)
Dot Gain: 25%
Separation Type: GCR
Black Generation: Medium
Black Ink Limit: 100%
Total Ink Limit: 238%
UCA Amount: 0%
Note that the Total Ink Limit is set to 238% to allow for a rounding error that could push black just over the 240% limit. Though not really a problem in itself, that might show up on Lightning’s radar.
Actually, if you’re Photoshop savvy, you can simplify this entire step, because I’ve already saved the settings for you. Download my color profile, unzip it, and install it in one of the locations checked by Photoshop. Then, for the destination space profile, instead of choosing “Custom CMYK,” choose “Lightning Source Cover CMYK (238%).” The profile is at
4. Click “OK” to exit each dialog box and complete the command. Your colors should now all fit within the 240% total ink limit.
5. All that’s left is to move the image back into the standard CMYK space Lightning wants, but without changing the ink coverage. Go to Edit > Assign Profile, or to Image > Mode > Assign Profile in older versions—not to Convert to Profile, which would put you right back where you started! For profile, choose “U.S. Web Coated (SWOP) v2” from the pull-down menu—or you can just click the button for “Working CMYK” if it specifies that profile. Then click OK.
Alternatively, you can use Assign Profile to choose “Don’t Color Manage This Document,” which will leave the image without any color profile. This should work just as well within Photoshop, as long as the Working CMYK in your color settings is U.S. Web Coated (SWOP) v2.
Don’t see much difference in color from when you started? That’s what you hope for! But most likely, you’ll see at least a slight loss of contrast, which is what happens when lower amounts of ink are applied overall. To some extent, you can adjust for this, but the time to do it is before you follow the steps above. Otherwise, you can push the colors back over the ink limit!
The preliminary adjustment I’ve found to work well is +20 Contrast in Photoshop’s Brightness/Contrast command—the current version of that command, not the “legacy” one. But you may have to experiment to get the result you want. To try different settings without converting the color space for each trial, you can use Photoshop’s soft proofing. In a custom proof setup, choose “U.S. Web Coated (SWOP) v2” as the device to simulate, and check “Preserve CMYK Numbers.”
The most reliable view of your cover, though, will of course come in a proof from Lightning. Can’t afford multiple file submissions and proofs at Lightning’s prices? Then you might consider first running off proofs at CreateSpace, which uses the same presses. Since CreateSpace doesn’t charge for file processing and doesn’t insist on overnight shipping, the cost of proofs is minimal. Just make sure you don’t accidentally start selling the book.
What about interior color pages? There’s no lamination here, so Lightning imposes no restriction. Still, there can be even more reason to limit your ink, because the paper quality is lower. Images that will print just fine on the cover can appear muddy when printed inside. So, you might try limiting the ink if you have graphics that are particularly dark and ink-heavy. But again, it’s best to wait and see results before deciding on such a drastic alteration.
Update, Sept. 2011—Recent reports indicate that Lightning may no longer be enforcing the 240% limit, or at least not as strictly. The kind of dark areas that normally occur within a photo, for example, now seem to be acceptable. So, it may be worth first submitting your cover as is, to see if alteration is really needed.
On the other hand, if your cover is mostly dark, you might want to impose the limit yourself, regardless of what Lightning does. Remember, Lightning’s reason for the limit is to prevent problems with the lamination. Publishers now report such problems with some covers from CreateSpace, which likewise uses HP Indigo presses for covers but does not impose the 240% limit.