I thought I should post this one as I have noticed during my time here that alot of you are unaware of this.
Everytime you save a jpg you lose data. If your processing your images and saving them as jpg each time............DON'T.
Each time a jpg is saved it loses data. It's called jpg artifacting (you may have heard of this). Your image will eventually become a mass of pixels. I recieive jpg logos all the time (even though a logo should be vector art i.e. an illustrator file) that people have resaved hundreds of times and I am expected to produce something decent out of them....No can do. Once a jpg has been resaved too many times it is stuffed forever, there is NO WAY to repair it. (you can try some ps work to help it a little but basically it's gone).
So here's what to do with your image:
1. Download from your camera
2. If working in format do your stuff and finally save as .tif
3. If is a jpg from camera save as .tif
4. Work on the .tif and save it as many times as you like
5. When you are happy with the image then save it as a .tif first for archiving, and save your .jpg for emailing, posting etc. That way you always have your original version to change later if you wish.
6. Bottom line, work in .tif format, then save as jpg.
Hope this helps you keep better quality images.