Ever since I launched The Illustrated Section, I have been getting a ton of questions by creators about what is the best size and resolution for PDF files intended for e-readers. Here’s some answers to these questions.
If you’re not designing for a specific device, I recommend you design your book for the iPad. Of the popular e-readers, it has the largest screen. If you format for the iPad it will look good on other smaller devices too, and you cover more bases that way.
First, it’s good to know the size of the device you are formatting for. The iPad screen is 1024×768 pixels. That means your images should be close to or bigger than this size if you don’t want them to look blurry.
For example, a page of my comic My Sister, the Freak is 7″x10″. When I formatted the PDF, I made the images 100 dpi so the pixel dimensions were 700×1000 pixels.
You don’t have to go much bigger than that. Even though my page size is technically smaller than the iPad screen, it looks great and the reader can even zoom in a little without it looking too pixelated.
My opinion for ebooks is you want to create an experience that is just slightly better than viewing your comic or book on the web (a standard web image is 72 dpi). For that, you don’t need a super high resolution. I generally recommend somewhere between 100-150 dpi depending on the size of your pages. Anything over that is probably overkill. It will make your file sizes unnecessarily large, which will make them tougher to download and read.
Another thing to take into account is the ratio of the height and width of your pages. You want to avoid anything extremely wide or extremely tall, because they will appear small when fit onto the screen, and will require lots of zooming and scrolling in order to read them. This could especially be a problem for picture books, which are often horizontally oriented and contain full page spreads.
That being said, I have found that your pages can be fairly wide/tall before it starts being super inconvenient. Just make sure your text is large enough to read and your images are clear when zoomed out.
Will Terry’s Monkey & Croc, for example, is made up of fairly wide horizontal spreads, but still looks great on the iPad.
Multiple Page Sizes
A typical comic or picture book might be best viewed one page at a time, but what if you have a couple pages you want viewed together as a full page spread? Or what if you have one or two horizontal pages in a mostly vertical book?
I advise to simply make your pages as they are intended to be viewed. Combine multiple pages in a spread together as a single page. And use whatever page size if best for each individual page. The beauty of digital books and PDFs is that every page doesn’t have to be the same size. Also, most e-readers are flexible enough to handle change in vertical/horizontal orientation where the reader just needs to push a button or turn the device to flip the screen.
If you’re afraid that making the reader flip or zoom in on the page might be inconvenient for them, I generally think it is not a big deal if it doesn’t happen too often during the course of the book. If you’re switching every other page however, then maybe consider changing the page size/design of your entire ebook.
One more tip – I have run across a few ebooks that have horizontal pages or spreads rotated in order to fit on vertically designed e-reader screens. I advise against this. Like I said above, most e-readers are smart and flexible enough to handle change in orientation and size. Rotating the images yourself will work against that, often to frustrating results. For example:
Here is a horizontal page.
The iPad is a vertical screen.
This is what the page looks like on that screen.
The creator thinks it would be smart to rotate the image to fit on the screen better. The reader buys the book and tries to read it. The file opens up and it looks like this:
So the reader rotates the iPad so they can read the page. But guess what? The iPad detects this and… rotates the page again. It turns out the reader can’t read the book at all unless they turn their neck and read it sideways.
This might not be an issue for all devices, but you never know how your reader is going to read your PDF or if their screen is horizontal or vertical. Just leave the images as they are and how they’re intended to be read.