I'm shooting in a studio, with unchanging lighting. When using the M Manual Exposure shooting mode, what are the best practices for adjusting the Aperture, Shutter Speed and Gain controls. Should I adjust them so that I get a full range on the waveform monitor? I previously tried the P mode, because it sounded easy as the aperture and shutter speed are automatically adjusted. However, when I tried this, the picture became very dark. I'm sure it was probably me somehow, but when I change to M, the picture brightens up significantly and I use half as much light in my softboxes. Just trying to figure out the right balance between the camera settings and the # of bulbs to use for optimum picture.