That's weird. Mine isn't that bad, but recently I noticed that the "Pop Art" effect on mine is only showing the yellow part of the photo (if I remember correctly, it usually has 4 quarters, each of a different colour).
So yeh, I restarted photobooth, but no change as of yet. I dunno why it's doing it. I don't use Photobooth much, but it's still annoying.😕