Many cameras today record photographs in roughly a 3:2 ratio. This means that the long side is 1.5 times as long as the short side. This is the reason 4x6 has become a popular print size. When we look through a viewfinder it is this size that we see and generally compose our pictures with. However, the ratios are not the same for all standard print sizes and that means you image will be cropped.
If you print an image to 5x7 or 8x10 size the ratios are different than the 4x6 format. Prints at the 5x7 size have a 3.5:2.5 ratio. The long size is 1.4 times as long as the short side. Prints at the 8x10 size have a 5:4 ratio. The long side is 1.25 times as long as the short side. It is often easier to think in terms of the length multiplication factors instead of the actual ratios.
The image of the girl playing in the dirt shows the different points where a 5x7 and 8x10 image would crop a 4x6 format photograph. This means that if you are shooting images (such as portraits) where enlargements are likely, you need to leave some extra room on the long side of your image so that important items are not cropped out of the image.
If you plan for the squarest ratio (the 8x10 print), you should almost always be able to crop a nice image out of your original in any format. Although many standard prints are not exact matches to one of these three ratios, few are below the 8x10 length multiplication factor of 1.25, so shooting for 8x10 format should allow room for nice crops.
- Standard Print Sizes and their length multiplication factors
- 4x6 - 1.5
- 5x7 - 1.4
- 8x10 - 1.25
- 10x13 - 1.3
- 11x14 - 1.27
- 10x20 - 2
- 16x20 - 1.25
- 20x24 - 1.2
- 20x30 - 1.5