Many of us, especially landscape photographers, will live with a polarising filter permanently fitted to a lens – which is generally fine if that fits your usual photography, but in the studio it’s more likely to act as a variable ND filter affecting your exposure making your images variably dark (you do use a light meter don’t you?).

Quite simply, a polarising filter will eliminate polarised light, but in doing so it will also eat between one and three stops of light. If you are using a light meter in the studio that means that your images are going to be dark (the amount of light eaten by the polariser may even vary with the orientation of the camera and could result in different degrees of underexposure when changing between portrait and landscape orientation).

So, if you are ever in the studio and your images are underexposed check that you don’t still have a polarising filter fitted!