Children's Book Formatting for the Kindle: Updates
About a year ago, I wrote a blog post that has become fairly popular about how to format a children's book for the Kindle e-reader platform. Technology moves forward, however, and that includes the technological wizardry behind e-books and e-readers. I felt it was appropriate to post an update to cover some important changes since that older post, and to address something that I did not discuss before (the dreaded "aspect ratio").
Screen sizes and display resolutions are increasing. Before discussing those things, it's good to understand what they mean. The screen size is literally just the physical dimensions of the display screen. Display resolution refers to how many pixels are crammed into those physical dimensions. Higher resolution is better. With one pixel per inch, you'd only get a handful of pixels into larger devices, and one meaningless pixel on a small device like a phone! (Note that this resolution is for the device, not a digital image file, which has no resolution – no, not even the mythical "72 DPI.") Anyway, I originally wrote that you would want to size your image so that it is 600 pixels wide. While this still works fine for many devices, it will not work as well on a Kindle Fire HD 8.9" which has a (portrait-orientation) screen width of twice that, i.e., 1200 pixels.
So what can you do? First, understand that scaling images (changing their sizes) works much better going down, to smaller sizes, than going up. When you scale up, the software doing the work must create image data that didn't exist in the original, and it can look terrible. Scaling down, the software handling it can just eliminate image data, which (usually) works out relatively well. Therefore, rather than target a smaller display, I would now recommend looking at existing displays, find the maximum, and then size images slightly larger than the current maximum. You don't want to go overboard with that, because larger files cost more to deliver. Also, you should target one specific orientation of the reader — that is, either landscape or portrait. Portrait (where the display is taller than it is wide) will probably give you better results, but that really depends on your book.
There are better – albeit more complex – options for what to upload to KDP than a ZIP file with an HTML file and JPEG images. While an HTML file with JPEG images in a ZIP file should still work, it does not give you the control or flexibility of a true eBook file. Now, if you really just want simplicity, you can try to get decent results from a Word file — but I don't recommend it. However, some people value simplicity on their end over value on the buyer's end, so that is a choice you could make. On the simplicity/value spectrum, I would put a Word file on the end with the highest convenience to the author and lowest value to the reader. Using an HTML file and JPEGs in a ZIP would be in the middle of that spectrum. If you want to maximize value for buyers, however, I recommend going to the other end of the spectrum by building a complete eBook file that includes the text and images of your book and "metadata" too. Metadata is data about data; in this case, information about your book that can be used by e-reader devices and apps to improve the presentation of your book.
There are multiple ways to build a complete eBook file, but one approach that offers a lot of flexibility is to create your book as an ePUB file, either manually or with an ePUB authoring tool such as Sigil. Not only can you load this into the Kindle Previewer software and export a completed Kindle file, you can also upload the ePUB to other e-publishing platforms, such as PubIt! (Barnes & Noble, for the NOOK platform), Kobo Writing Life (for the Kobo platform), and others. You can even sell the ePUB directly to readers who can view it in a wide variety of hardware and software tools. If you want to reach the largest possible audience with the least possible effort, ePUB is a sensible format to use right from the beginning.
Aspect ratio mismatches aren't new and aren't going away. One of the common concerns I've heard from people who are struggling to prepare their children's book for the Kindle is that the images don't fill the screen. And there, my friends, is an introduction to the "holy grail" of this type of project. I can promise you that, with current technology, you will not be "filling the screen" on every device readers could use to view your book. The reason for that? Aspect ratio mismatches.
Now, don't run away from the term "aspect ratio" just because it sounds strange or because the word "ratio" makes you think of math class. It's just the term for the ratio (or fraction, or decimal… more math terms, heh heh…) that you get when you compare the height and width of an image (or an image frame, whether that means an e-reader screen or something else). If your images is 50 pixels wide and 100 pixels high, you have a 1:2 width/height ratio (or a 2:1 height/width ratio). For every one pixel the image is wide, it is two pixels high. In other words, it is twice as high as it is wide.
The aspect ratio of a raster image (like a JPEG digital photo) can't change without changing the image itself. To change the aspect ratio, you could crop the image (i.e., slice off pieces along the full length of one or more sides) which would change how much of the image appears, or you could squeeze or stretch the image, distorting the contents. Without cutting away or distorting the image, though, you have to keep the same ratio, even if you change the size. Going back to that 50x100 example image, if you scale it down to 25x50 you still have the same 1:2 width/height ratio. If you scaled it to 30x50, however, you would end up distorting the image.
So… what does that mean, especially about Kindle book formatting and the as-yet-unattainable goal of filling the screen on every device? Well, different devices have different aspect ratios, but each image in your book can only have one. If you create the image for the aspect ratio of Device A, it won't fill the screen on Device B with a different aspect ratio. Typically, the device (or app) will scale the image down so that the entire thing fits on the screen, but because the aspect ratio is different, some of the display is left blank. Hopefully the illustration on the right side of this page helps to clarify this problem. You may be familiar with "letterboxing" on a TV, which is another situation caused by aspect ratio mismatches.
What can be done? One approach is to pick one specific device model to target and just accept that devices with different aspect ratios won't have their screens filled with your images. Or, instead of picking one device, you can pick a common aspect ratio (e.g., 4:3) and, again, accept that devices which have displays with different aspect ratios will not have their screens filled with the image. (It would be possible for a device to fill the screen by automatically cropping, but I have not personally seen this implemented and it's not a particularly good idea because important image content could be cropped off.)
Like the photo? Download the uncropped full-resolution original.
As I've mentioned previously, if you're not comfortable tackling these issues on your own, I can format your book for you. As technology continues to change I will be refreshing my knowledge for optimal book formatting, so if you're not keen on keeping up with those changes yourself, you can let me do that for you. On the other hand, once you get a feel for it, you may find that it's not that difficult and it's within your own capabilities. Many people learned to develop Web content on their own, and authoring eBook files is very similar to authoring Web content. However you go about it, I wish you the best of luck with your projects, and I hope you avoid the sharks in the publishing world who will charge you thousands of dollars for something you might be able to do for yourself for free.
About the Author
Stuart J. Whitmore is an author of fiction and nonfiction, as well as a photographer, technology developer, and more. If you enjoy reading his blog posts, you might also enjoy reading his books. Take a look at the books by Stuart J. Whitmore today, and download your copy of one that looks interesting to you!