Some of the photos I took of my recent Xamot, Tomax, Mindbender, etc. fan drawings were blurry, even though I took good pictures under natural light. GIMP wasn't doing it for me. I found this great site called
LunaPic that has an 'adjust focus' tool. It worked really well to make pictures clearer. I actually first discovered it, not for this, but because I had taken a bunch of photos of my kids with too much sun in the background so there were too many deep shadows. It was really good for editing those as well. Anyway, I went and replaced a few things with better versions.