Cropping Ratios

When you send your photos to be printed and get them back are you sometimes surprised to discover parts of your photo are missing?

You probably don't realize that the images you print are not necessarily in the same proportions as the images your camera takes.

Many (most?) cameras take a photo which is the same proportions as 35mm which is 3 by 2 written 3x2. Why? Because 35mm photos are really 35mm long by 24mm wide. Dividing both 35 and 24 by 12 gives (almost) 3 and 2. So a 35mm photo has a 3 by 2 ratio.

All 4x6" photos are 3 by 2 because if you divide both 4 and 6 by 2, you get 2 and 3. Now we really don't care if the answer is 2x3 or 3x2 - the difference is really just the difference between the photo being upright (portrait) or sideways (landscape).

The problems start when you print larger than 4x6". Standard print sizes are named for the sizes of paper that are produced. Four by six inch prints are named so because the paper is 4" by 6". Companies like Kodak produce paper in several standard sizes: 4x6", 5x7", 8x10", 11x14", 16x20" and 20x24". There are others but most of use don't use anything much larger. Some sizes of prints are standard because you can fit them onto one of the standard sheets. For example you can fit two 3½x5" prints onto a single sheet of 5x7" paper. And you can fit four 4x5" prints onto a sheet of 8x10" paper.

A 5x7" print means that you have to "crop" or trim part of the photo to make it fit the paper. As you can see in this photo of the Swiss guard, part of the image will be lost when it's printed. Why? Because if you divide 5 by 2½ to bring it down for our 2x3 ratio, the 7 comes down to 2.8. It's too small for the 3 in the 2x3 ratio. A 5x7 is a 2x2.8 ratio.

Likewise if you print an 8x10" print, dividing 8 by 4 to get 2 means that when you divide the 10 by 4 you get 2½ and overall you get a 2x2.5 ratio. As you can see in the image below, more of the top and bottom get clipped in the print.

Now it looks and sounds like a big deal and if your arithmetic isn't too good, the it probably sounds like a lot of gobbelldygook too.

But with two simple "rules" you don't have to worry at all.

First, always take your photos with a little extra room around the edges. This way when you crop your photos you won't lose anything important.

Second, don't let the stores crop your photos - do it yourself. If you use Picasa, you should crop your own photos. Double click a photo to enter the editing routine and choose the Crop button from the Basic tools. There you have the choice of cropping sizes.