Tutorial: Cropping Digital Images for Printing

Printing your digital images can be wonderful. And wonderfully frustrating. Dealing with a top-notch printing service eliminates a lot of the hassles. This tutorial is intended to arm you to avoid one source of frustrations that many people encounter along the way.

First, a definition: aspect ratio is the relationship of an image's width and height. 35mm film frames are approximately 24mm x 36mm, giving an aspect ratio of 2:3. Many common photo print sizes have different aspect ratios, however. For example, though a 4" x 6" print has an aspect ratio of 2:3 (matching the 35mm film), an 8" x 10" has an aspect ratio of 4:5.

When you print a digital image, the aspect ratio of the image is matched to the aspect ratio of the print size by either clipping parts of the image to make the image fill the entire printing area or adding blank white borders around the image to make the aspect ratio match the print size. If you care about the composition and form of your printed images, neither of these may be acceptable options.

Let's look at a couple of examples. Suppose that you want to print a typical 35mm slide scan at 4" by 6" inches. At this print aspect ratio, the raw scan should be in roughly the correct aspect ratio and hence should print without much of the image being clipped. On the other hand, if you print this same file to 5"x7" paper, part of the image will be clipped (or blank strips will be printed along the two short edges, depending on the practice of the printer).

The images below illustrate the effect of cropping. If cropping is done to a particular aspect ratio, some of the image area is lost. Since 35mm film is basically a 4" x 6" aspect ratio, this crop loses the least of the image. Note the rocks at the bottom of the image are lost in the 5" x 7" crop. When you get prints of your images, you can crop the images yourself or rely on the printing service to automatically crop them (as happens when you have prints made from negatives). The choice is yours to make!

Uncropped Image, with slide mount visible	Cropped Image (No aspect ratio enforced - slide mount removed)	Cropped Image (4"x6" aspect ratio)	Cropped Image (5"x7" aspect ratio)

If the important image contents are well away from the edges of the picture, you can just let your photo printing service crop the image automatically (just as you would have done if you had prints made from the 35mm negative) -- assuming that the printer offers this option.

If you care about parts of the image that are along the edges, you should crop the photo to the correct aspect ratio prior to uploading the images to the printer; careful cropping can assure that your prints contain the parts of the image that you care about. Additionally, you might want to crop and enlarge only a portion of the image. Having the images in digital form give us additional control that we didn't have with film (without additional expense or skill).

Cropping is easy to do with almost every photo editing package. We'll describe the steps to take if you have Photoshop Elements or Photoshop, but other packages should be similar.

1. Always work on copies of your images. If you save a file using the same file name after doing a crop or other editing, the original file that you opened is gone forever. Additionally, note that repeatedly opening, editing, and saving digital images in JPEG format results in degradation in image quality. Open the copy of the image you want to crop in your photo editor.
2. Press the letter "c" to activate the crop tool (or click on the crop tool in the toolbox).
3. In the options bar (at the top of the screen) enter the desired height and width. You can simply enter "4 in " and "6 in ", for example, for a 4" x 6" crop. (Do not put a number in the resolution field since you don't want the image resampled when you crop it.)
4. Click in your photo and drag out the rectangular cropping area. Photoshop will keep the ratio of height and width constant according to the values you entered into the options bar no matter how you drag the box.
5. When you have the area selected that you want to keep, release the mouse button.
6. You can fine-tune the crop by dragging the whole crop box by clicking in the center of the box and dragging, or by grabbing the resize handles on the outside to adjust the size. You can rotate the cropped area by moving your mouse pointer outside the border of the crop area and then clicking and dragging. Photoshop will enforce the aspect ratio.
7. When you are happy, hit the Enter (Return) key.
8. Save off your now cropped image (using a different file name if you don't want to lose the original!), ready for upload to a printing service. Done!

One other thing to note is that most printing services have a noticeable bleed area -- part of your image will be allowed to "hang off the sides" so that the printing goes all the way to the edge of the paper. Hence even images cropped to the correct aspect ratio will lose some of the image along each edge. The amount lost depends on the service being used. You may need to experiment a bit to see how your printing service behaves, though some of the services try to show you the effect online.

Questions on this procedure? Please let us know.