Aspect ratio settings in Picasa. Click image to enlarge.

Aspect ratio is the relationship of the width of an image to its height, of its horizontal to vertical dimensions.

Some digital cameras let you select an aspect ratio within the settings menu. The ratios match standard print sizes.

For digital cameras without this setting, you can crop images to the desired aspect ratio with editing software.

Why setting aspect ratio is important

If a photo doesn’t have the the same aspect ratio as the paper it’s printed on, one of two things happen. Prints will have an odd sized border on some sides or the printer will arbitrarily crop. To be in control of how a photo is cropped, it’s best to crop it yourself before printing.

All editing programs have tools for cropping at various aspect ratios. They offer pre-set sizes such as the shown for FastStone Image Viewer, an image browser and editor that is free for home users.

To maintain high visual quality when cropping images, shoot at the highest resolution and quality settings. Digital cameras with high megapixels produce images with areas that can be cropped more without a reduction in image quality.

Though not always possible, try to frame shots so they require a minimum of amount cropping.