Hi,
Sorry missed Tom's talk on .raw files, but if you are a Canon user then you can use DPP(Digital Photo Professional) to work on Canon raw .cr2 files and it will convert them to jpeg for you if you so desire. If you want to work on a file in photoshop or elements say to add a different sky then its normally best to convert the file to a 16 bit .tiff where it retains all the pixel/tone details and then finally save it as a jpeg ready to print.
There is a good article in EOS magazine at the moment about this. Jpegs are 8-bit images and the human eye cannot detect the millions of colours in 12 bit and 14 bit images that most Canon cameras store their images at in raw format, in fact the human eye can only detect a tonal range of 10-12million tones where an 8-bit jpeg produces in theory 16 million tones. The advantage you gain is that with raw you are working with all that colour information and when it is compressed and saved as a .jpeg then more colour detail is retained. Whereas when you start with a jpeg work on it and then save as a jpeg then you have lost some of that information. Its one of the reasons why the newer cameras have highlight tone priority, auto lighting optimiser etc, they store in raw form more colour information than the human eye can detect and thus can bring out extra detail. Dont forget though that you aren't going to see these 16-bit tonal advantages when you look at your monitor, because the monitor cant see them and neither can your eyes. Ok not strictly true, obviously if you use the highight slider it may well bring back information in a white sky that you couldn't see before, but i hope you get the drift.
Canon's DPP is free, it comes with the camera, but more important with every new camera it is updated and you can download the updates free, unlike Adobe Camera Raw which often entails you buying the latest edition of Photoshop etc, especially if you get a new camera. DPP now has a lot of adjustments, such as highlight and shadow detail sliders, sharpness or unsharp mask and one click will get you the correct white balance no matter what you set originally in camera.
You will also only gain when printing a 16-bit tiff file if your printer recognises the files and its highly doubtful it will. Most printers are 8-bit..
http://www.steves-digicams.com/knowledg ... nters.html for more info.
Shoot in raw, use dpp to edit the files and if you want to do some fancy stuff then save as a tiff to edit in photoshop etc, though its highly probable that unless you are doing loads of stuff on an image in photoshop you probably wont notice the difference if you imported it in as a jpeg, unless you printed it at A3 size or larger. You will get far problems with monitor, and printer profiles, but thats another long story.
Phil.