But each file format would have its own compression scheme. I believe you are referring to JPEGs, which allows you to change the compression level. I had replied a while back in a post about a way to go about doing this, and found it in the thread link below:

http://www.vbforums.com/showthread.php?t=370585

The method should allow you to specify a number from 1-100 to specify the amount of compression/quality when saving images as JPEGs