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Neutral Density Filters Absorptive ND Filters
Neutral Density Filters are solid neutral coloured optical Filter glass, using the absorptive properties of the glass to attenuate light. They have level spectral transmittance characteristics in the visible region 400nm to 700nm. To achieve the correct optical density or transmission each filter batch is polished to a stated desired wavelength until tolerances have been achieved.
The optical density equation:
D = log10 (1/T), or T = 10-D
Custom Sizes
Diameters: 4mm to 160mm
Squares/Rectangles: 1mm to 165mm
Thickness: 0.50 to 4.00mm
Dimensions/Thickness: to 0.02mm
Surfaces: 80/50 to 20/10
Flatness: up to Lambda 1
Parallelism: up to 1 min.
Transmission: to 2%
Absorbance: to 0.02mm
Density: To 0.02
Options
Transmission curve 400-1100mm
Absorbance curve 400-1100mm
Calibration certificates
Spot readings @ wavelengths
Identification labels
Storage boxes
Mounts & holders
AR coatings
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 Stock Neutral Density Filters – Absorptive
The Neutral Density filters are produced from glass types by Schott and Hoya. They are also mounted in housing and holders for use as calibration filters.
Optical Density Calibration
The filter accuracy of the absorbance is measured at up to six different values, using neutral density filters with calibration values traceable to the National Physical Laboratory (NPL), certificate reference no1545. The wavelength measurements were made at 510nm in the absorbance. Calibration of absorbance 0.005A or 1%.
 
Boxed sets available
For more information please contact us.
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