Please contact the technical staff before shipping instruments or standards to the address listed below.
Calibration services in this area provide access to the photometric scales that are realized and maintained at NIST. Lamp standards of luminous intensity, luminous flux, and color temperature, as well as reference photometers and materials as described below, are issued or calibrated on a routine basis.This laboratory's quality system is based on the ANSI/NCSL Z540-1-1994 standard and the ISO/IEC Guide 25.
NIST will issue to the customer 1000 W modified FEL quartz halogen lamps calibrated for luminous intensity (candela) and color temperature (kelvin). These lamps have a double coil filament and a clear bulb, and are potted on a medium bipost base. The lamps are operated at approximately 7 A/85 V dc, at a color temperature of 2856 K. The relative expanded uncertainty of the luminous intensity of these lamps is 0.6 % and the expanded uncertainty of the color temperature is 8 K at 2856 K.
NIST will calibrate the luminous intensity and color temperature of incandescent lamps with a medium bipost base submitted by customers. The inside frosted lamps, the airway beacon lamps, and the 1000 W FEL lamps previously issued by NIST can be submitted for recalibration. Customers can specify either the lamp current or the color temperature of the lamp (normally 2856 K) for calibration. The uncertainty of calibration is described above.
NIST will issue to the customer 1000 W modified FEL quartz halogen lamps as described in 37010C calibrated for color temperature. The lamps are usually calibrated for a color temperature of 2856 K. The expanded uncertainty of the color temperature of these lamps is 8 K at 2856 K.
The color temperature standard lamps issued for 37030C can be calibrated for additional color temperature points in a range from 2000 K to 3200 K. The expanded uncertainty of this calibration is 4 K to 11 K in the range from 2000 K to 3200 K.
NIST will calibrate the color temperature of incandescent lamps with a medium bipost base submitted by customers. The inside frosted lamps, the airway beacon lamps, and the 1000 W FEL lamps previously issued by NIST can be submitted for recalibration.
NIST will calibrate the total luminous flux (lumen) of incandescent lamps and fluorescent lamps submitted by customers. The standard lamps previously issued by NIST can be submitted for recalibration. Miniature lamps may also be accepted. Customers should contact NIST before submitting lamps. The relative expanded uncertainty of this calibration is typically 1.0 % for incandescent lamps and 2.0 % for fluorescent lamps, which depend upon the reproducibility of test lamps.
NIST will issue flashed opal glass plates, 51 mm x 51 mm, calibrated for luminance coefficient (ratio of luminance/illuminance, unit: sr-1) for International Commission on Illumination (CIE) Illuminant A (2856 K source). The glass plates, masked with a circular aperture 25 mm in diameter, are calibrated for the luminance within a circular area of 1 cm in diameter in the center of the aperture. The relative expanded uncertainty of this calibration is 0.8 %.
NIST will calibrate luminance (cd/m2) of submitted sources or the luminance coefficient (sr-1) of submitted transmitting diffusers, including opal glass previously issued by NIST. Customers should contact NIST before sending sources or diffusers. The relative expanded uncertainty of luminance calibration is 0.8 %.
NIST will calibrate photometers, illuminance meters, and luminance meters submitted by customers. Calibration is usually made with the CIE Illuminant A (2856 K incandescent source) in a range of 0.1 lx to 3000 lx for illuminance and 0.1 cd/m2 to 4000 cd/m2 for luminance. The relative expanded uncertainty of calibration is 0.5 % for illuminance and 0.7 % for luminance at normal levels, which will increase at low levels. As an option, NIST can measure the relative spectral responsivity of submitted instruments and calculate spectral mismatch correction factors for a source of known spectral power distribution. Illuminance calibrations at a level up to 100 klx can also be made under a special arrangement.
NIST can provide special tests for sources, detectors, and photometric instruments other than those stated above under limited conditions by special arrangements with NIST. Customers should contact NIST for consultation.
NIST will calibrate submitted flashing-light photometers to measure integrated illuminance [lx . s] or effective intensity [cd]. Calibration is normally performed with white light (~6500 K) from a xenon strobe light in the range of 1 lx . s to 100 lx . s and with red light using an Aviation Red filter. The relative expanded uncertainty of calibration is ~1 % or larger depending on the performance of the instrument under test.
NIST will calibrate submitted colorimeters or spectroradiometers for chromaticity coordinates (x,y) of several colors of a display. The instrument under test will be calibrated against a NIST reference spectroradiometer, using a standard CRT display or and LCD, or any other display submitted by the customer. The calibration will be performed for the primary colors (red, green, and blue) plus white of the display, and a correction matrix for the Four-Color Method will be provided, which can be used to correct the errors for any other colors of the display measured with the test instrument. The expanded uncertainty (k=2) of the calibration is typically 0.001 to 0.002 in (x,y) depending on the color and display type.
NIST will calibrate submitted Light Emitting Diodes (LEDs) for luminous intensity (CIE Averaged Intensity A and B in candela) and/or total luminous flux in lumen. For luminous intensity, 5-mm epoxy type or other LEDs that have an alignment fixture can be accepted. For luminous flux, LEDs having luminous flux higher than 0.1 lm can be accepted. Test LEDs are operated with a specified current at ambient temperature of approximately 25 °C. The relative expanded uncertainties (k=2) of the calibrations are typically 1 % to 3 % for luminous intensity and 1 % to 2 % for total luminous flux, depending on the color and reporducibility of the LEDs. Further calibration capabilities are under development.
NIST Measurement Services: Photometric Calibrations, Y. Ohno, Natl. Inst. Stand. Technol. Spec. Publ. 250-37 (1997).
Improved Photometric Standards and Calibration Procedures at NIST, Y. Ohno, J. Res. Natl. Inst. Stand. Technol., 102(3), 323-331 (1997).
The Detector-based Candela Scale and Related Photometric Calibration Procedures at NIST, Y. Ohno, C. L. Cromer, J. E. Hardis, and G. Eppeldauer, J. IES, 23 (1), 89-98 (1994).
National Institute of Standards and Technology detector-based photometric scale, C. L. Cromer, G. Eppeldauer, J. E. Hardis, T. C. Larason, and A. C. Parr, Applied Optics, 32 (16), 2936-2948 (1993).