Home / Products / Optical Filters / Neutral density filters

Neutral Density Filters

ND filters

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

Special Properties

  • Color-neutral transmission
  • Absorptive filters
  • Largely linear transmittance
  • Transmission and density depend on the thickness
  • Almost independent of the incident angle

Typical Applications

  • Attenuation filters
  • Filter optics for light measurement
  • Measurement standards
  • Optical attenuator for sensors
  • Exposure correction filters for photography
  • Camera lens filter
  • Light-level control filters
  • Attenuation filter for laser power meters

Related filters, coatings, and information

Request for Quotation

 

Neutral density filters are also commonly referred to as ND filters, gray filters, OD filters, or optical density filters. Neutral density filters provide nearly constant, color-neutral transmittance and show minimal dependence on the wavelength of the incident light within a wide spectral range. This enables precise control of light levels in optical systems. 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 density is determined by test measurements of a raw gray filter material, which is then ground and polished to a thickness slightly above the calculated target thickness. When this thickness is reached, measurements are taken again, and the filter material is polished down further if necessary. In this way, the target value is approached as closely as possible.

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. Each set is manufactured individually. 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:

 

Request for Quotation

 

Specifications


Optical transmissions of
SCHOTT NG filters at 1 mm thickness

NG 1, NG 9, and NG 10
NG 1, NG 9, NG 10 grey filters, transmission curves
Display NG1, NG9 and NG10 transmission


NG 3, NG 4, NG 5, NG 11, and NG 12

NG 3, NG 4, NG 5, NG 11, NG 12 grey filters, transmission curves
Display NG3, NG4, NG5, NG11, and NG12 curves

 

Please refer to our online calculator for all SCHOTT color filter materials, which allows you to perform individual filter transmission calculations.

Table of NG Filter Transmittance

(Defined for 546 nm at 1 mm filter thickness)

Type

Transmittance
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

  • SCHOTT neutral density NG filter materials
    (unpolished filter sheets)

Thermal Tempering

  • Minimum thickness for full tempering = 3 mm

Flatness

  • Depending on material and thickness
  • Other qualities per request

Surface Quality

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

Maximum Dimensions

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

Further detailed filter characteristics are available on request.

*The production of NG 10 and NG 12 neutral density filter materials has been discontinued. We only have a small stock of those materials left.


All data and specifications given are average guide values and are not guaranteed. Moreover, please consider the “Notes on Specifications”.

 

© 1994 – 2025 Präzisions Glas & Optik GmbH

Last update: October 14, 2025