I learned about the very cryptically named c2g GEGL operation in Gimp from this post at the Linux Photography blog. I like to convert soft wide-open photos to black and white, but I’m not always happy with the results – when I increase the contrast to get the black parts like I want the transitions between black and white often get weird and eroded. c2g doesn’t always work well, but I especially like it when I blend a c2g’d layer back into the original image – the results remind me of colorized Civil War era photos. Here’s a before-after, the first with just a levels adjust and the latter c2g’d and blended back in.
I certainly wouldn’t recommend doing this to every photo, but I’ll probably at least give it a try now and then.
