Adobe Photoshop : File size

Managing file size is important when working with digital images. If you don't keep track of your file sizes you may end up with very large images, and this will undoubtedly cause problems somewhere down the line: large files eat up disk space quickly, crash printers, slow down web browsers, and take much longer to edit in Photoshop. Do everything possible to keep your file sizes as low as possible!

The size of a file (measured in bytes) is related to its physical dimensions (the size at which it prints); when you decrease the physical size of an image, the amount of memory used by that file also decreases (all other things being equal).

You can check the amount of memory a particular file uses by using Windows Explorer on the PC, or by opening the folder in which the file is contained on the Mac. You'll see the name of the file and its size in bytes (Don't know how to do this? See the Orienting Yourself in Cyberspace tutorial).

To check the physical dimensions of an open Photoshop file:

Choose Image>Image Size.
A dialogue box like the one below will appear with the size and resolution. Size is usually given in both pixels and inches (you have the option of changing these units). Note: Pixel units are useful when sizing images for the web.

You can change the image size by changing either size or resolution. Just type a new value in each box; if you want to resize the image proportionally, check the "Constrain Proportions" box.