[jethsy]

I have just heard that editing photos compromises their quality. I use Picasa and sometimes GIMP for editing. Usually, I don't do the SAVE in Picasa after editing, so I assume the originals are intact in My Pictures. I want to know more about this issue. Any help you give will be appreciated. I'd like advice on the best practices with photos because I do some editing to just about every one I take.
Thanks!

[Ent]

This depends upon the file format which you save under. The effect is most noticeable with Jpeg images because of the way in which they are compressed. If you repeatedly open, edit, save, and close a Jpeg the quality will start to degrade. To avoid losing any quality, it is better to save intermediate work in the specific format for your program; in the case of Gimp it's XCF. Then once the picture is finally finished you can save it as a Jpeg for the compression benefit and delete the XCF file. The degradation of one saved edit will not be noticeable and won't even be comparable to the changes from editing in the first place.

[hewee]

Almost every image format that can compress the image will have a option to change the compression that is by default compressing the image about 30% so always check out any options.
You may need to use and you should anyways use the SAVE-AS and always add a number to the image name your saving.

[jethsy]

Thanks so much! I think I can summarize from your answers that doing one edit (cropping, lightening) will not compromise the photo's quality enough to notice. Tell me if I am wrong.
Thanks for the tips!

[Ent]

Saving the edit is what causes the quality to degrade, but one save should not compromise the quality enough to notice. If you want to do more than one edit you should do them all before you save the changed image as a JPEG.

Remember that the edit itself can still go either way and you need the skill to judge which look your after. For example lowering the brightness to black out an image or excessively blurring the photo might be bad for the quality of the picture. Undo is a very useful feature!