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 newly developed 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 in case 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:
NG 1, NG 9, and NG 10 ND-filters
Enlarge transmission curves
Please use our online calculator for all existing optical glass filters from SCHOTT for individual filter transmission calculations.
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.
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