Weekly Writers: Ebook Covers

Don't be square

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Ebook covers are a jpg or png file (though if the latter, they shouldn’t include transparency). They are always rectangular and in portrait orientation (images that are taller than they are wide), rather than landscape (wider than they are tall). The ebook cover image is what will appear as a thumbnail (small version representing the book) on vendor sales sites such as Amazon, and at full size on e-reader devices and ebook software.

The actual pixel dimensions of the image are not fixed. Over time, services will require higher resolution images, because the screen resolution of digital devices also increases. It’s generally better to aim high, then scale down if required. That’s a useful guide for all graphics work: you can remove detail from a picture if it isn’t needed, but you can’t easily add it in. Think of a photo at a low resolution of 800 x 600 pixels. It only takes moments to rescale it to 640 x 480 and will look just as crisp, only smaller. Whereas if you enlarge it to 3200 x 2400 you will have a huge, blurry mess.

Aspect ratio refers to the relationship between the dimensions of one side, and the dimensions of another; width and height. We’re used to seeing it when discussing screens on TVs, monitors and phones. 16:9, for example, means that for every 16 pixels along the horizontal edge, there will be 9 pixels on the vertical edge (which gives us a wider landscape orientation). An aspect ratio of 1:1 would be a square (as used on audiobook covers, where 3000 x 3000 is the current standard).

But aspect ratio is not the same as resolution, or the number of dots in an image. Let me explain.