I have both the Tiffen 47 and 47B filters. I used them outdoors when I want a white sky and good shadow detail. Both will darken skin tones. B+W makes a medium blue filter, but it is not that strong, with a filter factor of 2x. B+W also makes a special-order blue-green filter, which I have. The number is 470 and the filter factor is 2x. It absorbs almost all red light. Use it to simulate ortho film.(posted 8763 days ago)