Filters picture
Home / Products / Optical Filters / Neutral Density Filters

Neutral Density Filters, Optical Density Filters, ND-Filters

SCHOTT NG Filter materials

Special Properties

  • Light radiation absorbing
  • Neutral in color
  • Linear transmissivity
  • Transmittance depends on thickness
  • Transmission is independent from the incident angles

Typical Applications

  • Colour neutral attenuation filter
  • Neutral density filter applications
  • Light measuring filter
  • Measuring standard optics
  • 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 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 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 raw material. The raw ND-filter material, is then ground and polished to the calculated target thickness and re-verified. This way, the transmittance of the final ND-filter is adjusted.

A neutral density filter is often used for exposure correction in front of a camera lens in photography. It is used to attenuate the incident light that enters the camera lens to an acceptable level for a correct exposure. 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-Filters, which are all absorbing neutral density filters, can be calculated with our easy-to-use online application.

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


To request for quotation of neutral density filters made of any SCHOTT NG 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 546nm at 1mm 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

  • min. filter thickness for full tempering = 3mm


  • 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

  • 164mm (square shape)
  • 150mm (diameter shape)

Further detailed filter specifications on request.

Please consider our "Notes on technical specifications"