I’m working on covers for my e-books and I’ve realised that there is a lot of confusion about the size and resolution of the images that are required. Part of this confusion is caused by the companies that sell these e-books, they often change the sizes of the images that are displayed on the website, less often the sizes of the covers that are actually used on the e-book itself.
Then there is additional confusion caused by the software used to design the covers and a lack of understanding about what DPI means. DPI literally means Dots Per Inch, it is only important if you are printing an image, in the world of print (which I have limited experience of, having only worked as a print designer on a few projects) it is usual to work to a standard of at least 150 Dpi, many printed images are set at 300 Dpi. This means that if you are printing an image of 600×600 “pixels” then it will be only a 2 inch square. In web design the dpi of the file is completely irrelevant, the only Dpi that is important is the Dpi of the monitor that it will be viewed upon. Back when I started working in web design this was, invariably, no greater than 72 dpi, these days the iPhone 4’s retina display has a dpi of 326! In short dpi is utterly irrelevant unless you are printing an image, even then you have to be printing the .PSD rather than the .Jpeg for the dpi to even be associated with the image.
Right, so DPI set aside as a none issue, since I am creating .jpeg covers what are the actual sizes that are required?
Amazon E-book cover and promotion image sizes
Since I’m worrying mostly about getting my Kindle edition ready at the moment I’m talking simply about the Kindle and Amazon sizes.
Books are generally taller than they are wide, so when expressing a pixel size these generally reflect this. The accepted standard for any co-ordinate or dimension measurement is width(the X axis) x height (the Y axis), my old maths teacher explained this as “you have to go into the house, before you can go up the stairs”
Catalogue size: A minimum of 1000 pixels on the long side and a ratio of 1.6
(625×1000), but it recommended that the longest side be 2500 pixels (1562×2500).
Cover sizes and internal images: Kindles currently support a maximum resolution of (600×800) in 16 shades of grey and a maximum file size of 147Kb. Which is pretty big for most purposes.
So I’m going to work with a new PSD file with a width of 3124 and a height of 5000 pixels, this should make my images pretty future proof, but will allow me to output the .jpegs in the appropriate sizes with the minimum of fuss.