If your camera supports a RAW image format you should try using it. When the camera convert images into jpeg, it discards the information that it used to build the jpeg. If you save files in the RAW format, you retain all of the original information from the CCD of your digital camera. Having this, you can often create much better pictures on your computer.

If you want to do this, add RAW support in Ubuntu is easy, just type the following on the command line:

sudo apt-get install gimp-ufraw

If you are using the gimp, then restart it. Now you can open images in the RAW format and you can adjust then before they get placed in the Gimp.