When I'm saving a JPG file, Paint Shop Pro (Windows) and Gimp (Linux) show a pop-up to choose the JPG compression level. The apps have something like 85 as default value, and I think reducing the image quality in exchange for a smaller file size made sense bank in 1996 or perhaps even in 2006.
What would a sensible compression level be today?
This is not about high-end lossless photography, nor about small graphic files for web sites — I'm editing vacation photos made with a regular digital compact camera. Given that the photo files are already JPG format, I want to keep as much quality as possible without switching file format (because all the apps work with JPG). The file size is 2-5MB per photo and I don't care if the file sizes are 10% bigger or smaller - disk space is not a concern, but picture quality is (although not professional-level).
My understanding is that saving a JPG file with "85" reduces the quality, while "100" retains the quality of the original (which doesn't mean it's perfect either).
Why should I choose the default value "85", or why should I choose "100" instead?