I’m a techie. I use the Debian distribution of Linux with KDE, Firefox, and Thunderbird. I also use the Gnu Image Manipulation Program, or simply The Gimp. It’s a great program with tons of features that can do just about any kind of image manipulation you want it to do, and fairly easily at that. It’s also free, and available for Windows and Mac! If you’ve got a point-and-shoot digital camera and want to do some editing, basic or advanced, on your photos, then this is the program you want to get.
Unfortunately, Gimp is (currently) limited to 8-bits of information per color channel. Support for 16-bit and 32-bit color information is not expected until v3.0 which is not expected any time soon. Whether this is important to you depends on the source of your images and what you want to do to them. If your source images are JPEG, then they’re only 8-bits (per channel) to start with so being able to edit in only 8-bits is just fine. If, however, you have a digital SLR or film scanner that outputs in TIFF or RAW (called NEF by Nikon and other names by other manufacturers) with 10, 12, 14, or 16 bits of information per color channel and want to do editing that will make significant changes to color, contrast, or brightness and you want to display this in a professional or semi-professional setting (like hanging 8x10s on your wall), then (and only then) might you need something more.
Enter Adobe Photoshop. This is the première photo editing software. Every professional uses it. It was the first and it is the best. It’s also US$650, but an older version of it may have come free with your camera or scanner.
I’ve recently rescanned the photos in my gallery using a Nikon Coolscan IV at 12-bit color because I wanted to be able to make some minor changes to the exposure and still have full tonal range for printing poster-size images. This meant switching to Windows and loading up Photoshop for all the color correction. Once that was done, I could save it and switch back to Gimp for cropping, sharpening, spot healing, etc. At least, that was my plan. Since I was in Photoshop, though, I decided I’d use it for those things instead.
To make a long story short, they’re both very capable programs. Yes, Photoshop has more and some of its tools (like lens correction) are better and/or more polished than any Gimp equivalent. Switching between the two is not difficult; the biggest problem is finding the tool you want since they’re not in the same place in both programs and sometimes have different names or icons.
Of note, photoshop has an incredible “spot heal” tool which fixes errors due to dust, scratches, or hot/dead pixes in your image. You just paint the damaged area and presto-chango, it’s fixed. Color, texture, and grain are all preserved just like there had never been a problem. It’s not just smoothed-over; it’s generated based on information around the area. What a fantastic tool!
On the other hand, I could not get Photoshop to fix some perspective problems with one of my pictures. I won’t say that it can’t do it (that would be foolish) but the “Lens Correction” filter always made something else worse while making the perspective better. With the Gimp “perspective” tool, I just dragged one corner of the image and clicked “transform”. Done! Nothing could be easier.
In conclusion, I was able to do all the same basic editing functions in either program. Both are excellent works with similar ease-of-use. Photoshop has a few more features, a bit more polish, and 100x the 3rd party support… the vast majority of which you will never use or even notice missing. Don’t waste your money on it until you know you need it, then accept no substitutes.