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TECHSPEC® components are designed, specified, or manufactured by Edmund Optics. Learn More

2.5 OD 25mm Diameter, Reflective ND Filter

Stock #43-811
Qty 1-5
Qty 6+
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Angle of Incidence (°):
Surface 1: Inconel
Diameter (mm):
Optical Density OD (Average):
Reflection (%):
Surface Quality:
Thickness (mm):
1.60 Nominal
Transmission (%):
Neutral Density Filter
Blocking Wavelength Range (nm):
400 - 700
Substrate: Many glass manufacturers offer the same material characteristics under different trade names. Learn More
Float Glass
Dimensional Tolerance (mm):
Clear Aperture (%):
±5% of Optical Density
Optical density values are average over specified blocking wavelength range.
Surface Flatness:
4 - 6λ

Regulatory Compliance

RoHS 2015:
Reach 219:

Product Family Description

  • Spectrally Flat
  • Maximum Accuracy and Neutrality at Moderate Price
  • Use Stacks to Create Intermediate Density Values

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.

Optical Density exhibits an additive relationship; for example, stacking filters with OD values of 0.6 and 0.9 yields a resultant density of 1.5. The optical density is related to the transmission by the following equation:
T = 10-OD x 100 = Percent Transmission.

Reflective Neutral Density Filter Kits

Reflective Neutral Density Filter Kits are available with either 8 or 14 optical densities. The kits with 8 filters include our most popular filters, with densities of 0.3, 0.5, 1.0, 1.3, 1.5, 2.0, 2.5, and 3.0. The kits with 14 filters include all available densities, except for 3.0. Kits are ideal for determining precise system optical density requirements. Custom densities are available for OEM applications.