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Spectral Reflectance and Transmittance


NIST maintains the national scales for reflectance and transmittance in the ultraviolet, visible, and near-infrared spectral regions (250 nm to 2500 nm). Our primary objective is the dissemination of those scales and the advancement of SI-traceable reflectance and transmittance metrology.


NIST serves as the nation's primary source for spectral reflectance and transmittance measurements from 250 nm to 2500 nm. Our reflectance and transmittance measurements support the measurement infrastructure of communities involved in optics, photonics, color technology, instrument manufacturing, pharmaceutical, healthcare, coatings manufacturing, and remote sensing. NIST also supports the measurement services of our nation's military standards laboratories and interacts with its peers at nation metrology institutes through international intercomparisons.

Neutral density filters for comparison measurements.
RTS (Reference Transmittance Spectrophotometer)


NIST offers world-class calibrations of spectral reflectance and transmittance through NIST Calibration Services at the NIST Storefront. The catalog of available calibrations includes Green filter transmittance, Spectral tests of spectral reflectance, and Special tests of spectral transmittance. For some services, the measurement parameters are customizable, within the limits of our capabilities. Pricing is based on actual costs, labor and time, and various measurement parameters. Each calibration results in a calibration report is issued, which includes the calibration values and uncertainties for the customer-supplied test item(s).

Wavelength Standards

NIST previously offered calibration of holmium oxide glass under the Service IDs 38050C and 38051C. However, based on NIST's extensive experience with holmium oxide glass and its long-term stability, NIST no longer sells or recertifies this standard. These standards have shown insignificant spectral variation from batch to batch and from one manufacturer to another. More information can be found in the paper, Holmium Oxide Glass Wavelength Standards. Transmittance and absorbance data from this paper can be download as an Excel file (404 kB).

Major Accomplishments

ROSI (Robotic Optical Scattering Instrument)

NIST continually strives to improve its capabilities for providing these measurements and add to the general knowledge by performing research on related topics.

Created February 12, 2021, Updated April 11, 2023