Originally Posted by STL
Circular one is the one you can adjust right?
B+W brand filters are all adjustable (meaning you can rotate them on the lens), but from what I understand some of the linear filters can effect your autofocus and metering negatively on your camera. They will work fine in one instant, but in another, they will keep your camera from focusing. The circular filters have an extra filter behind them to allow more light to shine in so the camera can focus and meter accurately.