A mystery solved. Filenames on Canon EOS cameras, like the T2i, 60D, 7D, etc all use the pattern IMG_xxxx.JPG or IMG_xxxx.CR2. One day I noticed all the filenames on my Canon T2i started with an underscore replacing the ‘I’, so they started with ‘_MG_xxxx’. I didn’t know what I had done but wasn’t worried cause it helped distinguish them from the photos from my Canon 60D.
Today I found the answer while browsing the user’s manual for my camera (oh the horror!).
If the image is captured with the color space set to Adobe RGB, the file name will start with “_MG_” (first character is an underscore).Yep, I had changed the color space on my camera to Adobe RGB from the default sRGB one night and forgot. Since I shoot almost exclusively RAW, and color space only affects JPG images, I never noticed the difference.
For now I will go back and set it the sRGB. I know Adobe RGB is ‘better’ quality but not all browsers are smart enough to display Adobe RGB files correctly, and the only reason I would shoot JPG is so that I don’t have to process the image.
Hope this helps someone else’s quandary!