If your image is high resolution, it’s fine for print, right? Not necessarily.
Here are some rules of thumb on image resolution:
• Photos need to be high resolution at the size (dimensions) they will be printed to look good on paper — typically, 300 dpi. A postage-stamp sized image won’t look good printed at 3 x 5 inches even if it’s hi-res. If printing on a digital press or using images that are ghosted back, you can get away with a slightly lower resolution.
• When using a digital camera, make sure it is set to shoot the photos at maximum size. And using a higher quality camera will give you better images for print.
• When purchasing stock photography, buy the large size. Then you can downsample the images for web use, which requires only 72 or 96 dpi.
When you enlarge an image, its resolution is reduced by a corresponding amount. So a 300 dpi image blown up 200% is effectively a 150 dpi image, which means it will come out less crisp in print. It’s usually safe to blow up an image about 10% without seeing a loss in quality. Keep in mind that images with hard edges or high-contrast areas will be less forgiving. You’ll see a pixelated effect along edges and in fine detail, such as the guitar strings above.
If you have a high-quality image that needs to be produced at a large size, Chicago Press can help with specialized software. Give us a call.
Text and Line Art
With text and line art from vector files, resolution is not an issue. Vector is the best format for most logos, charts, and drawings. Vector graphics are geometric descriptions that do not get converted to pixels until the printing plate is made, which is typically 2,400 dpi. That’s why vector line art and text prints sharper and cleaner than the typical pixel-based line art or text.
If you must scan or create text or line art in a raster/pixel program such as Photoshop, work at a higher resolution, such as 1200 dpi, to get a better printed result. A drawback to this is that you end up with very large files that are cumbersome to work with. Vector images are much smaller and almost always print more sharply than raster images, even those at 300 dpi (like the one on the right below, shown in contrast to a vector image on the left).