The B+W +4 diopter close-up lens is the right power for additional close-up range with the 50 mm lens (up to approx. 1 : 3) when the B+W +2 close-up lens has reached its limit. This is the maximum power for telephoto lenses with focal lengths of 85 mm (to approx. 1 : 2.1) and 100 mm (to approx. 1 : 1.9), but you should stop down to at least f/8.