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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 and density depend on the thickness
  • Almost independent from the incident angle

Typical Applications

  • Color neutral attenuation filter
  • Light measuring filter optics
  • Measuring-standard
  • Light attenuator for sensors
  • Exposure correction filters for photography
  • Film camera lens filter
  • Attenuation filter for laser power meters

Related filters, coatings and pages

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There are several different designations for neutral density filters. Such radiation absorbing filter optics are also called ND-filters, grey filters, OD-filters, or optical density filters. Neutral density filters are absorbing filter optics. They have a nearly constant transmittance which is mostly color-neutral and almost independent from the wavelength of the incidence light over a wide wavelength range. A significant advantage of absorptive density filter optics is that their transmittance does not strongly depend on the incidence angle unlike it is the case for most filters based on optical coatings. The attenuation of an absorbing ND-filter depends on the filter's thickness. The suitable NG grey-filter material and the appropriate density is selected under consideration of the desired target light transmittance, which is defined for the wavelength of 546nm (see table). Hence, almost any required filter density and therefore its transmittance can be adjusted by setting 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 entering the camera lens to an acceptable level, so that correct exposure is achieved even when a lot of light enters the camera lens. 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 any SCHOTT color glass filter. Also, the transmittance spectra of any NG-grey-filter material 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 density specifications and requirements. Please send us your inquiry in case you want to order an ND-filter set.


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


Request for Quotation


*The production of NG10 and NG12 neutral density filter materials has been discontinued. We only have a small stock of those materials left.



Light transmissions of SCHOTT NG-filter materials
at 1 mm glass thickness

NG 1, NG 9 and NG 10 ND-filters

NG 1, NG 9, NG 10 grey filters, transmission curves

View optical transmission curves

NG 3, NG 4, NG 5, NG 11 and NG 12 ND-filters

NG 3, NG 4, NG 5, NG 11, NG 12 grey filters, transmission curves

View optical transmission curves

For specific filter transmittance calculations, please use our online-calculator for all optical glass filters from SCHOTT.

Light Transmittance of NG-Filter types
defined for 546 nm and 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 Filter 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. 80-50 scratch & dig (MIL-0-13830A)
  • Other quality available on request

Maximum Dimension

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

Further detailed filter characteristics on request.


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

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