If you create Kindle illustrations with much larger dimensions, they’ll look amazing on Fire HD and HDX and still look great on Paperwhite, Kindle DX and older eInk devices.
I’m convinced that targeting the high resolution HDX instead of the lowest common denominator is the better path to follow.
Before ignoring the conventional wisdom to use a maximum width of 600 or 800 pixels for broad compatibility, I experimented with a set of images at various sizes and concluded that important diagrams, charts, and wide illustrations display beautifully in context and when zoomed on Kindle Fire HDX 8.9″, Fire HDX, Fire HD, Paperwhite and Kindle DX at a maximum width of 1600 pixels. This size gives HDX 8.9″ the pixels it needs to display images with text or critical details in the viewing area or zoomed to full-viewport width.
Gardyloo! A maximum width of 600 pixels is out the window. My new maximum width for Kindle images is 1600 pixels.
Why do images look too small on the HDX?
HDX Kindles have a higher pixel density than the Fire HD or eInk Kindles. All of them have a higher pixel density than your PC.
The more pixels crammed into a square inch, the smaller the image appears on screen. Simple as that.
The table of screen densities shown below is derived from Amazon’s Screen Layout and Resolution documentation:
|Kindle Device (Gen)||Generalized Density||Actual Density|
|Fire HDX 8.9″ (3rd)||xhdpi (320DPI)||339dpi|
|Fire HDX 7″ (3rd)||xhdpi (320DPI)||323dpi|
|Fire HD 7″ (3rd)||hdpi (240DPI)||216dpi|
|Fire HD 8.9″ (2nd)||hdpi (240DPI)||254dpi|
|Fire HD 7″ (2nd)||hdpi (240DPI)||216dpi|
|Fire (2nd)||mdpi (160DPI)||169dpi|
|Fire (1st)||mdpi (160DPI)||169dpi|
Why does using larger images work?
Kindle automatically scales down images proportionately to fit the screen, and they look fine. Conversely, it’s unwise to scale images up because that will cause blurring and pixelation. If Kindle HDX 8.9″ has enough pixels to be happy, your work will look spectacular on the higher resolution devices down to eInk models. The only image characteristic that looks wonky on my old Kindle-3 is gradients; they display obvious banding when rendered in 16 shades of gray.
Danger Will Robinson — don’t make every image enormous!
Some images, such as nice but non-essential mood-setting art at the beginning of each chapter will look silly when too tall or too dominant. If such images are round or square, versus wide rectangles, they will look better at a maximum size of between 400 and 800 pixels in diameter, depending on the image. You might also want to experiment with making chapter-top images all the same height, allowing the width to vary. This strategy can work if your illustrations are similar in shape.
Large rectangular photographs
Huge photographs will be way over the file-size limit of 127 KB and too tall at 1600 pixels wide. Some photos can be cropped down to a “panorama” of about 400 pixels in height if the most interesting part of the composition can be extracted as a narrow band. Landscapes are well-suited to this treatment, a large rectangular or squarish photo, not so much. Unless you want a full-screen image, make the image short enough to display the lead-in or following sentence on the Paperwhite and Kindle HD.
Tall narrow illustrations
Be careful with portrait-oriented images that are tall and skinny because they will scale vertically to fit the viewing area and may become too narrow to retain essential details or readable text. Infographics or maps might need to be rotated sideways or even split in two for usability on smaller screens. It would be wise to test such images using an older version of Kindle Previewer or by sideloading on an old eInk Kindle (3rd Generation would be fine, I think) before publishing. Make yourself a very short book with a few test images and some dummy text to speed things up. Kindlegen will convert the book without a cover, but a content.opf file will be necessary. Use Sigil or Calibre to add the content.opf, toc.xhtml and toc.ncx files with a few clicks.
To view a .mobi file on your Kindle, connect the device into your PC using the USB cable. View folders and files. The Kindle will appear as a drive on your PC. Drag the .mobi file into the Kindle’s Books folder (Documents folder on Kindle 3). Eject (Kindle 3) or disconnect (Fire). Now you can read the file on your Kindle until you want to delete it.
In any case, review the appearance of images on all device simulations available in Kindle Previewer and on your own Kindle(s) and Kindle eReaders. There’s a great deal of wiggle room, personal preference, and commonsense involved in choosing image sizes. For chapter-top images the goal is to find a sweet spot between the image size that looks dinky on the HDX and the one that looks way too big on the Paperwhite.
Rule of Thumb
If you feel gobsmacked by an image, follow your instincts and make it smaller until it looks about right on all the devices available in Kindle Previewer. Take the time to test and experiment before working on your final proof to avoid having to publish more than once. Creating vector illustrations makes it easier to resize images without loss of quality. In Photoshop, make your original images at the biggest dimensions you think you’ll need and work on copies for radical size changes. Use Smart Objects whenever feasible.
Use vector images for making line drawings, diagrams, and charts. If you have Adobe Illustrator, it’s easy to create images as native .ai files and Save for Web as PNG for the Kindle version and Export to TIFF for print. Such images have a small file size and edges appear quite smooth. To reduce file size, save as PNG-8 if possible. Images with complex gradients or special effects may need PNG-24 or JPEG.
Remember that Kindlegen transforms PNG-8 images into GIF and PNG-24 to JPEG. It will compress JPEG images to about 50% quality even when under file-size limits. Text generally stays clearer in GIFs than in JPEGs.
Photoshop is better for editing photographs. Type already set in Illustrator can be placed in Photoshop as a Smart Object, if it suits your workflow. Of the 34 illustrations in my book project, twenty-eight were PNG-8, five were PNG-24, and one was a JPEG. If you work with an author who wants to include concept drawings or clipart in a book file, use vectors and save as PNG-8 or GIF to keep the book down to a reasonable download size.
For the cover, you’ll want to go all out with whatever file format is best suited to the job. Photoshop is great for covers including photos, overlays, background images, and gradients. Illustrator is suitable for covers with creative typography, shapes, and line drawings. Create the cover at 300dpi or higher so that if you or your client decides to do a Createspace version, you’ll be all set with an illustration that fits the Createspace template with minimal tweaking.
Screenshots from Kindle Previewer
The following images are from Kindle HD, HDX, HDX 8.9″, Paperwhite, and DX. Click to view large images:
Note that Paperwhite honors the implicit KF8 (not amzn-mobi) media query and Kindle DX honors the Mobi (amzn-mobi) media query, centering a full-screen image. The oldest eInk Kindles expand every image that’s half the pixel-width of the viewing area to full-screen. For Kindle DX, the tipping point is 372 pixels. (For Kindle3, 311 pixels is the magic number.) You can accept this behavior or make separate images for old Kindles and hide them with CSS. I don’t think elaborate workarounds are worth the trouble for Kindle DX, which was discontinued and resurrected, probably not for long. For Kindle 3, the images will scale down to fit and look just fine.
Plan ahead for the print version
Pixel dimensions count in ebooks but resolution is important if you plan to publish a print version on Createspace. To avoid resolution issues, create the images at 300dpi, so all you’ll need to do in Word is figure out the size you need for your page layout. In the book I was working on, I scaled 1600px-width images down to 1275 pixels horizontally for a 6 by 9 inch layout. At this size Word could save them at 300dpi and display them at 100% without resizing when converted to PDF.
Once the images are the correct size for print, you can use them for a full color edition or export them as grayscale TIFFs for Createspace “black and white” interior pages.