Features

• Variable and 8-Step Versions Available
• Ø50 mm Filter Wheel
• Compatible with Our SM1 Lens Tubes and 30 mm Cage Systems

These new circular neutral density filter wheels are compatible with our SM1 (Ø1") Lens Tube and 30 mm Cage Systems. NDM1 and NDM3 are eight-step ND filters while NDM2 and NDM4 are continuously variable ND filters. The ND filter wheel is attached to a rotating lever arm so that it can be moved out of the beam path; angular gradations are printed on the rotating axle, thus allowing it to be repositioned at precisely the same location. In addition, an #8-32 (M4) tapped hole is provided in the base to allow for post mounting.

Calculation of Optical Density (OD):
The optical density is given by

OD = log₁₀(1/T) or alternatively, T = 10^-OD

where T represents the percent transmission. Note, that when defined this way, the optical density is synonymous with absorbance. For the NDM1 and NDM3, which are 8-step ND filters, the appropriate percent transmission values are provided in the following table: