re: adjusting while I'm out there ... that's the thing -- I won't be there. I need to be able to set up the camera to take the photograph in situations where I can't be on-hand. (But perhaps NDRS has a programmable human he can donate to the cause ...)
re: lens ... the more I think about it, the more I think a condensor is needed. The diffuser is going to be at least a half-inch across, maybe twice that. The photoresistor is roughly .12" in diameter. Without a lens, most of the light passing through the diffuser won't hit the photoresistor. Yes?
Most incident light meter has the dome diameter approximately 3/4 inch and yet the diameter of the photocell is 1/2 inch or less and there is no lens.