Here's a biggie: you do not have to photograph on the least compressed setting when you photograph JPG to get the best image quality! I normally photograph weddings and portraits of groups of 3 or less in medium JPG on my Canon 20D. You will not be able to tell the difference regardless of how large you print between the "high" and "medium" settings!
Why? Because you are still taking all the information from the sensor and it is being oversampled. I did not realize this until I spoke to my friend, Claude Jodoin. Claude is a technical editor and contributor to several professional digital imaging magazines, as well as an equipment tester/reviewer. He told me to try it on a wedding with 2 cameras. So I took (back then) 2 Canon 10D, and shot the altar groups twice: once with a camera set at High JPG and the other set at Medium JPG. I then returned to my studio and made a file 16x20 @ 268 dpi. I printed an 11x14 section of this image on my Fuji 4000 printer. The two prints were indistinguishable!
