When you format an ebook, or pay someone to format an ebook, you want a file that looks good on the eReader, is easy to deliver, and of a sufficiently small file size not to cost you any more money than necessary or cause problems when you upload it to vendors. In my work with authors, I’ve found the biggest barrier to the last item are the images used.
Now, before we go any further, I’m sure some of you reading this will think that I’m saying you can’t have any images. No flourishes at the start of each chapter. No swirls as scene breaks. I’m here to tell you that you can have a decorative eBook file that looks great and doesn’t take up much space.
Why is the last part important? Because honestly, a lot of people don’t think about the size of their eBook file. I hear from authors all the time that their file is excessively large and often the sites they use have a limit of about 10MB or so for ebook files. This is often the case in boxed sets where there may be multiple covers within the book. Often it’s not the chapter flourishes that cause the problem. And in fact, many of them can be created by embedding fonts, so it’s not something to worry about much.
The biggest culprit in this is the cover image. Since I do my own cover, I don’t usually run into a case where I don’t receive a low-resolution image of the cover, but since I’ve purchased a few as part of author projects, as well as simply talking to authors, I’m finding that many cover designers aren’t providing a low resolution image. And many authors don’t know how to convert their image using Photoshop or Gimp or another program into a lower resolution.
I, like many cover artists, develop the images at high resolution. Not only is it easier to work with, but you get a cleaner, prettier file. However, while images in printed form need approximately 300 dots per inch (dpi) in order to look good, a 72-96dpi resolution on most devices is sufficient. (Obviously with high definition and retina displays this may not be the case.) Lower resolution image files are smaller and they still look good.
The biggest tip I can give someone when formatting their book is to use a low resolution cover image within the file itself. If you use a lot of interior images (like additional covers), then use low resolution images. Not only will Amazon charge you less of a delivery fee, but if you upload your book to vendors, you’ll be sure to be within their file size limits.
The other place I make sure to use the smaller images are in the teaser material in the back of the book. In this way, I don’t have to worry about the chapter header images and I still obtain a reasonable file size.
The next time you’re having a cover done, ask for a low resolution image just for these purposes, and if you’re having an eBook formatted, check the size. Anything over a few MBs probably means that there’s some work your book formatter could be doing, and isn’t.