Cropping, which is the process of trimming unwanted parts of a picture off, is one of the most important tools for most photographers. It can mean the difference between poor or slightly off composition and the perfect shot. Although often used by amateurs and professionals, we occasionally fail to keep in mind the photo's height and width ratio that will be required when you go to print and frame it. Unless you will be using custom size frames all the time, which can get very expensive unless you make them yourself, you might want to make sure that this ratio is proportionate with that of the frame size you will be using. Otherwise you may find that you have to chop off more of the height or of the width of your photograph than you expected in order to frame it properly. You can determine the dimensions using good old high school math (didn't you know it would eventually come in handy one day?).
Cropping for Framing
While you don't really need to pay too much attention to your height to width ration when cropping an image for a website unless you have a very particular need, cropping a photo which you intend to print is a complely different story.
Here is a formula that you can use to determine the optimum height and width of a photo so that it matches your print format perfectly:
Photo Height Frame Height Photo Width Frame Width
Just plug-in 3 out of the four numbers and then do a crisscross calculation. For example, if you want to figure out the height of your photo, just do:
Photo Width X Frame Height ÷ Frame Width = Photo Height
To determine the width, use:
Photo Height X Frame Width ÷ Frame Height = Photo Width
Follow though the equation and you will see the crisscross pattern I am referring to.
The cropping tool in Photoshop can also help you accomplish the same results without having to do any math at all. Check out this tutorial over at PhotoShopEssentials.com to find out how.
I highly recommend you create preset crop ratios for various frame sizes as you will likely use them a lot. It only takes a few seconds to learn how to do this by checking out the "Create and Use Crop Presets" section of the article entitled 5 Secrets of the Photoshop Crop Tool.