This is the type of ND filter to reduce the transmittance by reflecting the incident light.
These filters have constant density values across the surface. The transmission to reflection ratio varies with density selection. In stacks, the total density is the sum of each filter’s density. ND filters are used primarily for the attenuation of light over a wide spectral range. They are often used in laser and photometer applications, where excessive power can cause damage or inaccurate results. Orient mirrored side toward source at 0° angle of incidence.
| ATTRIBUTE | SPECIFICATIONS |
| material | Float glass |
| DIAMETER TOLERANCE | +0.2, -0.2mm |
| parallelism | < 3 arc minutes |
| CLEAR APERTURE | >90% |
| SURFACE QUALITY | 40/20 scratch and dig |
| flatness | 2-4 λ subject to the size |
| od tolerance | +/-5% |
| COATING | 1st surface metal coating |
