Quote Originally Posted by Submeg View Post
Sure I get your point Harrison, but the thing is there are benefits over certain types. For example, say I was saving an image. Working in paint (of course) I would need to save it as BMP, if I wanted to modify it again, without it going blurry. If I was to stick it staight on the web, I would use JPEG if I was to create an animation file, GIF. But I see what you are saying about PNG....I use that, so much smaller than JPEG and I cant see the difference
PNG is lossless - it won't lose any quality compared to the original BMP. GIF is also lossless but limited to 256 colours. JPEG on the other hand is lossy.

The basic rule of thumb is PNG for diagrams (which are 'simple' enough for PNG compression to be effective) and JPG for photos (as two pixels are rarely the same in a photograph).