I have a text that includes images. Now, from what I've read, we are supposed to save these images at 300 dpi at a width of around 500 pixels. That, however, is what confuses me. If I save the image using those specifications, then it measures only 1.67 inches in width. Isn't it going to be miniscule on the Kindle screen? Yes, at the current resolution used by Kindle, the image will be bigger than 1.67, but it will still be quite tiny and, if they do start publishing at 300 dpi, the image will undoubtedly be incredibly small. If I opt to save the file at a more reasonable inch-based measurement, then the pixel width greatly exceeds 500 pixels. Can someone please tell me what I'm missing?
Okay, but their requesting that we future-proof the file at 300dpi is still extremely silly because, if they ever include a print capability, then the images that the reader can print will be unbelievably small. Also, what role does screen resolution play in all this?
Oh, and is the 500 pixel recommendation for image width even still correct or is there some other width that we should be sizing to now? I thought it might have changed since the dimensions for the cover were updated some time ago.
You need two different sets of images if you publish an ebook and a paperback book. If you publish a paperback (or hardcover), your images should be 300 DPI and sized exactly as large as you want them on the printed page. When you publish an ebook, it's the pixel count that you want to optimize, and in this case DPI is irrelevant. The ereader screens come in a variety of sizes; what pixel size will be appropriate depends on which device you are targeting (and whether you want your picture to fill the screen or just part of it). 600 by 800 pixels used to be a common recommendation, but some of the newer ereaders have larger screens now. On the other hand, the greater the pixel count, the greater the memory of the file size (which affects the KDP royalty).
I know that I need two images: one for print and one for Kindle. The part that had me confused was that the Kindle guidelines state that we should optimize our images to 300dpi. I'm guessing so that if they ever add a print function, the images will be of a high enough resolution. That, however, would result in very tiny images based upon the pixel measurements that we are confined to using.
Okay, so, suppose that I am optimizing for the Kindle readers and Fire. What pixel width would you recommend?
According to the KDP help pages, "An HTML image with an aspect ratio of 9:11 automatically displays with maximum screen coverage." However, 9:11 is pretty square, and the Kindle Fires are very tall and narrow. The Kindle Fire screen is 3:5 and HD is 5:8. A picture that matches these aspect ratios won't perfectly fill the screen, though, due to internal margins (which can even be adjusted by the reader). If you make a picture 3:5, it might fit the Kindle Fire's tall, narrow shape, but then it might look rather funny on other ereaders with squarer screens. If you make the picture more square, it will leave a gap above or below (or beside in landscape view) the image on the Fire. You might look into the Mobipocket creator. I believe you can use this tool to automatically fill the screen, for example. (If a single image completely fills the screen on any ereader, though, in some cases the aspect ratio must change significantly, distorting the image.) This tool may also add a little memory to your file size.
KF HD 8.9" is 1200 x 1920
KF HD 7" is 800 x 1280
KF is 600 x 1024
Kindle Paperwhite is 758 x 1024
Kindle Keyboard is 600 x 800
Kindle DX is 824 x 1200
Kindle Touch is 600 x 800
Kindle 6" is 600 x 800
But then the iPad is 1536 x 2048 and the Surface is 768 x 1366, for example.
Nothing is better than seeing your own images firsthand. You can get some idea by putting a variety of images in a "test" file, going to your bookshelf, adding a new (test) title, choosing a DRM setting, and uploading your test file (later, you can delete the title from your bookshelf). The previewers will offer some idea.
Amazon's recommendation for some time has been 600x800 pixels wide and tall. I don't think I have ever uploaded an image as hi-rez as 300 ppi. Most are 72 or 100 ppi.
In most (not all) Kindle devices and apps, an image was resized to fill the page.(I think the exception was Kindle for PC, which showed small images as small.) Alas, with the advent of the Fire HD and especially the iPad Killer tablet, we could no longer trust Amazon to do this work for us. Some people went to a larger image, say 1000xwhatever. Others recommend simply putting width=98% in the in-line style. (I am sure it can be done more elegantly in the style sheet, but I haven't played around with that yet.
Note that in the Fire HD you can zoom any image by clicking on it. In my case, with the smaller Fire HD, I find that even the lowest-rez images (450x550 at 72 ppi) enlarge beautifully to fill the page. I haven't tried this on the iPad or the iPad Killer.