Unravelling the mystery of making book covers

If you’re intending to self-publish – or supplying a picture to your publisher that might be used in a print edition, the three terms you’re most likely to hear are ‘bleed’, ‘CMYK and ‘resolution’.

A professional book cover.
A professional book cover.

They sound suitably mysterious but – as always – there’s no particular secret to them. And they apply both to potential cover photos and interior pictures.

Bleed – the printed content that spills over the intended final edge of the page, typically by about 3mm. This means pictures or background run cleanly to the edge of the finished page after it’s been trimmed. If you’re printing to a standard like A4, running ‘full bleed’ means using over-size sheets (‘supplementary raw format’/SRA, defined by ISO 217:1995 standard). That usually costs. But it’s worth it. The alternative is ending up with that “photocopier look” – the white edge where the ink doesn’t quite reach.

CMYK vs RGB – by default, images on a computer are RGB (red/green/blue) which displays by projected light on your monitor. Print, however, involves reflected light on paper and requires a different system – cyan, magenta, yellow and black. An RGB picture has to be converted to CMYK before it’ll print. Modern software often makes that switch for you, but be careful. Free utilities that can do it include GIMP and Irfanview. I use the latter all the time.

Resolution – Printing usually pivots on a resolution of 300 dots-per-inch (118.1 dots-per-cm), and you’ll often hear people ask for ‘print resolution’ or ‘300 dpi please’.  Actually that’s misleading – it’s not enough to simply supply a picture at that resolution. The photos I publish on this blog are typically 650 pixels wide, which translates to 5.5 cm. Not enough (and yes, I do that deliberately). In fact, the “dots per inch” is irrelevant. What counts is the number of pixels over a given linear measure.

It works like this. If you’re trying to make a picture meet a standard Royal Trade book cover (C5 = 16.2 cm wide x 22.9 cm deep), you’ll need a minimum of 16.2 x 118.1 = 1,913.22 dots wide. To that you’ll have to add 100 dots for the bleed. Conveniently, a 10 megapixel camera shoots roughly this along the short edge of the frame, so a picture of this size (about 4.5 mB) will print OK. Inconveniently, a cover also needs allowance for the depth of spine and any wrap-around to the back, if the design’s intended to do that. Most books do, these days.

Have you ever wrestled with this stuff? Does this post help? I’d love to hear from you.

Copyright © Matthew Wright 2014


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9 thoughts on “Unravelling the mystery of making book covers

  1. When I did the cover and interior pix for The Struggles I have to say it was pretty easy. Amazon Kindle has a program to help you through the process which is user-friendly and efficient. When I used the corresponding program in CreateSpace for the print edition of the book it worked out pretty well, too.

    From my perspective the major problem with covers and cover art, especially if you want to use pictures, is being sure that you aren’t stubbing yourself on someone else’s copyrighted toe. For The Struggles I was able to use pictures I took myself, but later on this year when I publish my novel I’m going with US Government photos.

    I’m going to take a look at Irfanview, Matt. Thanks for the tip!


    1. Yes, copyright license is absolutely the biggest issue. Irfanview is excellent. Its shareware and does all the key things you usually need with photos. Also handles batch processing.


  2. An excellent post Matthew – informative enough for the technically-minded to do their own while scary enough to drive the rest to ask someone like me to design a cover for them. Nicely-played, sir!


  3. I took a graphic design/marketing class in college and learned about these terms. It’s strange to think that the education of some of these is lessoning, with the move to more and more digital publishing. I liked linked in’s april fool’s joke : http://blog.linkedin.com/2014/04/01/announcing-linkedin-cats-you-may-know-connecting-felines-one-paw-at-a-time/. I commented to a coworker that a lot of people probably didn’t get the reason for the colors. He gave me a blank stare. He didn’t know either.


    1. There are a lot of skills and knowledge attached to print publishing that seem to have gone by the wayside – I guess they’ll always be around but will become more niche than anything else. I didn’t go into colour matching – though that could be next.


    1. Sounds very exciting though – these covers usually have a book attached to them & I am definitely standing behind a lot of other people in the queue waiting for your & Holmes spy novel! 🙂


      1. Thank you for your encouragement. We were supposed to have two out by now, but life happened while we were making plans. At this point, it looks like fall for at least one of them. Helps to know people are interested. 🙂


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