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Neutral Density Filters

Optical density ND-filters

SCHOTT NG 1, NG 3, NG 4, NG 5, NG 9 & NG 11

Special Properties

  • Color neutral
  • Absorbs light radiation
  • Largely linear transmittance
  • Transmission and density depend on the thickness
  • Almost independent of 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 information

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There are several designations for neutral density filters. Such filter optics are called ND-filters, grey filters, OD-filters, or optical density filters. Neutral density filters have a nearly constant color-neutral transmittance and are almost independent of the incidence light wavelength 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 what is the case for most filters based on thin-film coatings.

The suitable NG grey filter material and the appropriate density are selected under consideration of the desired target light transmittance defined for 546 nm (see table). Hence, almost any required filter density and transmittance are adjusted by setting the chosen ND-filter material's thickness. 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. 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 the camera lens for exposure correction. The filters attenuate the incident light entering the camera lens to an acceptable level to achieve correct exposure, even when much light enters the camera lens. Moreover, significantly extended long-term exposures are possible. Using our online calculator, you can calculate the transmittance spectra of any NG-grey filter material and any other SCHOTT filter with our easy-to-use online application.

We manufacture OD-filter sets according to your density specifications and detailed requirements for laboratory use or reference measurement applications. Please send us your inquiry if you want to order an ND-filter set.


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


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Optical transmissions of
SCHOTT NG filters at 1 mm thickness

NG 1, NG 9, and NG 10 ND-filters
NG 1, NG 9, NG 10 grey filters, transmission curves
Enlarge 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
Enlarge transmission curves

Please consider using our online calculator for all existing optical glass filters from SCHOTT for individual filter transmission calculations.

Table of NG-Filter transmittance

(Defined for 546 nm at 1 mm filter 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

Filter materials

  • Unpolished SCHOTT neutral glass filter material:

Thermal Tempering

  • Minimum filter thickness for full tempering = 3 mm


  • Depending on material and thickness
  • Other qualities are available on request

Surface Quality

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

Maximum Dimension

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

Further detailed filter characteristics are available on request.

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

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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Last update: May 21, 2024