As you can see, this is a photo of (one of) my guitar, a Gretsch Tennessee Rose. Now, I lit it with one lamp off camera-right and slightly behind the guitar itself to get the highlight, and I used posterboard to reflect some of it back as fill. The problem is the reflection of said posterboard (and my darkened room) in the knobs. To those with a bit of lighting experience, how could I go about fixing this? Moreover, if it can't really be helped with the kind of exposures that are neccessary with non-flash lighting, a theoretical explanation would be just as helpful. Any ideas, to cut down on that reflection while still keeping it under-exposed enough for the effect?