Being the regular user of Mac OS X, I just want to have a way of converting the file formats of the screen shots I take very often, since the default image file format that is being saved on the desktop for each screen shot I take using the Mac short keys (Shift+Cmd+[3 or 4]) will be PNG. So instead of changing the file format of the screen shots every time manually, I found a better way of converting the file formats as we desire automatically by just typing the following command in the Mac terminal window:

defaults write com.apple.screencapture type image_format Here replace the 'image_format' with the desired file format. I have tried with JPEG, TIFF and PDF and all the worked fine for me) You'll then have to logout/login to make the change take effect.