Multiple filters

[12pmc]

Hello - need some advise on filters (screw in) with B&W Negative

Where two filters are combined - are both the filter factors added togeather to calculate exposure, or does the combination of two filters require a more sophisticated metheod of getting the corrrect exposure?

If one filter is a ND and the other colored (Red for example) does it matter which filter is placed closer to the lens?

Thanks
Peter

[Jerry Bodine]

My understanding, as read from previous postings on this forum, is that the filter factors should be multiplied; filter corrections measured in stops, however, should be added. I don't believe it matters which filter is closest to the lens, except if a polarizer is in the filter stack it should be farthest from the lens front element. It should be noted that the manufacturers' filter factors are only a starting point and, because different films and light meters respond to colors differently, some personal tests are necessary for precision.

[Jim Jones]

When a polarizer or ND filter is used in conjunction with a color filter, the filter factors are as Jerry states above. Using multiple color filters can get more complex. I wouldn't worry much about the stacking order of the filters.

[Heroique]

Filter A, 1 stop comp, so filter factor = 2x
Filter B, 2 stops comp, so filter factor = 4x (or 2x2)
Filter C, 3 stops comp, so filter factor = 8x (or 2x2x2)

Final number of stops of compensation = 6 stops (or 1+2+3)

Final filter factor = 64x (or 2x4x8)

Personal testing will probably lead you away from these numbers.

[vinny]

Fwiw, with motion picture cameras and lenses that cost more than cars, the polarizer (round)is always closest to the lens in the stack (rectangular) and that's how the equipment that holds them is designed.

[12pmc]

Thank you to you all for the data.

Peter