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Neutral Density Filters

Optical density- and ND-filters made of
SCHOTT NG 1, NG 3, NG 4, NG 9, NG 10, NG 11 & NG 12

Special Properties

  • Neutral in color
  • Absorbs light radiation
  • Largely linear transmissivity
  • Transmittance depends on thickness
  • Optical transmission is almost independent
    from the incident angles

Typical Applications

  • Colour neutral attenuation filter
  • Neutral density filter applications
  • Light measuring filter optics
  • Measuring standard
  • Ligth attenuator for sensors
  • Exposure correction filters for photography
  • Film camera lens filter
  • Attenuation filter for laser power meters

There are several different designations for neutral density filters. They are also called ND-filters, grey filters, OD-filters or optical density filters and are defined as radiation absorbing optics. Neutral density filters have a nearly constant transmittance, which is largely color neutral and almost independent from the wavelength of the incidence light over a wide wavelength range. A great advantage of absorptive density filters is, that their transmittance is independent from the incidence angle, unlike this is the case for most coated filters. The attenuation of an absorbing ND-Filter is depending on the filter's thickness. The suitable NG grey filter material with the appropriate density is selected by considering the desired target light transmittance, which is defined for 546nm for all NG-filter materials. Hence, almost any required transmittance can be adjusted by defining the thickness of an ND-Filter. In practice, the transmissivity is determined by test measurements of the grey filter raw material which is then ground and polished to the calculated target thickness and re-verified. This way, the transmittance of the final ND-filter is adjusted.

Neutral density filters are often used for exposure correction in front of a camera lens in photography. By using it to attenuate the incident light that enters the camera lens to an acceptable level, a correct exposure can be achieved even if a lot of light is entering. For the conversion from density to transmission and vice versa, we provide our "Optical Density <-> Transmission" converter program on a separate website. Likewise you can use our newly developed online calculator for the calculation of the transmittance spectrum of all SCHOTT color glass filters. Of course also the transmittance spectra of all NG-grey filters can be calculated with our easy-to-use online application.

For laboratory use or for reference measurement applications, we manufacture OD-filter sets according to your specifications and requirements. Please just send us your inquiry if you want to order a ND-filter set.


To request for quotation of neutral density filters made of any SCHOTT NG grey filter material, with individual dimensions and transmissivity requirements, please click the button below

Request for Quotation


*The production of NG10 and NG12 raw material has been discontinued. We only have a small stock of those materials left in stock.



Light transmissions of all SCHOTT ND-filters
at 1mm thickness

Light Transmittance at 546 nm at 1 mm thickness



NG 1 10-4
NG 10* 0,004
NG 9 0,04
NG 3 0,09
NG 4 0,27
NG 5 0,54
NG 11 0,72
NG 12* 0,89

Raw Materials

  • SCHOTT NG1, NG3, NG4, NG5, NG9, NG10* and NG12* unpolished filter raw material

Thermal Tempering

  • minimum filter thickness for full tempering = 3 mm


  • Depending on material and thickness
  • Other available on request

Surface Quality

  • typ. typ. 80-50 scratch & dig (MIL-0-13830A)
  • Other quality available on request

Max. Dimension

  • 165 mm x 165 mm (square or rectangle shape)
  • ΓΈ 160 mm (diameter shape)

Further detailed filter specifications on request.

Please consider our "Notes on technical specifications"