Some images are okay to use in books and others are not. There are three general criteria to consider:

  1. Does the content and composition of the image add value for the reader (even if the value is purely decorative)?
  2. Is the image legally available to use?
  3. Is the image of a technical quality that can be successfully printed?

3. Is the image printable? The number one confusion I find with clients who submit photos they want included in their books has to do with image resolution. A picture that looks fine on a computer monitor at 72 or 96 pixels per inch turns into a jagged, pixilated mess when it is printed on paper. Learn to inspect the properties of any image you want to print. If you want it to be three inches wide on paper, the image needs to be at least 900 pixels wide (300 pixels per inch). The size of an image in pixels is called the resolution, and when someone says they need a high-resolution image, they mean they want lots and lots of pixels—at least 300 pixels per inch of final size. You can start with more and reduce the resolution successfully. Going the other direction (starting with a few pixels and faking an increase) almost always results in unsatisfactory results.

Brightness, contrast, and other overall characteristics can be manipulated to some extent. But if you start with a very poor image, it is unlikely that you’ll end up with a great one. On the other hand, if you begin with a photo that looks great hanging on the wall, it is going to have to be manipulated to look its best printed in a book. Every printer provides guidelines on adjusting the tonal range of an image for their presses. It is the compositor’s job to compensate for what’s called dot gain—the tendency of a dot on the printing plate to print a little bit larger. Fortunately, modern software makes this a pushbutton operation, but omit that step at your peril.

Finally, remember that line art (diagrams, cartoons) has to start out at much higher resolution than photographic images, typically 1,200 pixels per inch, to prevent jagged lines on the page.

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[Brian Jud invited me to contribute short articles on book interior design to his Book Book Marketing Matters newsletter, a biweekly e-zine. This page is adapted from one of those articles.]