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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 transmittance
  • Transmission depends on thickness
  • Almost independent from the incident angle

Typical Applications

  • Colour neutral attenuation filter
  • 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. Such radiation absorbing optics are also called ND-filters, grey filters, OD-filters or optical density filters. 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 does not strongly depend on the incidence angle, unlike it 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 and the appropriate density is selected under consideration the desired target light transmittance, which is defined for the wavelength 546nm. Hence, almost any required transmittance can be adjusted by defining the thickness of the chosen ND-Filter material. In practice, the transmission is determined by test measurements of a raw grey-filter material which is then ground and polished to a calculated target thickness and that is then measured again. This way, the transmittance of the finalized ND-filter is adjusted.

Neutral density filters are often used in photography in front of a camera lens for exposure correction. The filters attenuate the incident light that enters the camera lens to an acceptable level, a correct exposure can be obtained 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 a quotation for 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 filter material has been discontinued. We only have a small stocks of those materials left.



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


Light Transmittance at 546 nm / 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 squares

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

Maximum Dimension

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

Further detailed filter characteristics on request.


All given details and specifications are mean reference values and are not guaranteed. In addition, please consider our "Notes on technical specifications"