USDA/AMS is the most general source for visual color standards for fruits and vegetables and offers a catalogue of color comparators and equipment they have available.
FAQ: “…. the schema of the principle of measuring shows other way of light (source of light -> sample -> sphere -> detector) than our ColorQuest (source of light -> sphere -> sample -> detector). Please can you explain me difference between both construction? difference between both results of measuring?”
FAQ: “Straight from the LSXE Pro-forma, the LabScan XE sample ports are described as:
Port Insert, 3-mm illuminated area; 5-mm measured area
Port Insert, 6-mm illuminated area; 10-mm measured area
Port Insert, 13-mm illuminated area; 17-mm measured area
Port Insert, 25-mm illuminated area; 30-mm measured area
Port Insert, 44-mm illuminated area; 50-mm measured area
I always thought that the measured area was smaller than the illuminated area. Have the illuminated/measured area in the Pro-forma been transposed? Seems like it!”
Contrast Ratio Opacity measurement quantifies how opaque a sheet sample using two readings. One reading is taken with the black glass or light trap backing the sample at the port. The second reading is taken with the sample backed by a white tile or the white sample clamp insert. EasyMatch QC will prompt you for the proper backing when taking opacity measurements.
For measuring the brightness of some materials, some dated industrial methods cite a Magnesium Carbonate block standard to be set to Y = 100% in reflectance. This is a very old top-of-scale standard and HunterLab does not recommend using it.
The USDA quality system assigns peanut butter quality rating of USDA Grade A, Grade B and Other based on 4 attributes that total 100 points.
HunterLab does not supply glass or plastic filter transmission standards but here are some sources.
HunterLab sphere instruments with CIE d/8 geometries conform to the requirements of ASTM D1003 Section 8: Procedure B Spectrophotometer. The measurement of transmission haze using Procedure B instruments will be in close agreement with ASTM D1003 Procedure A Haze meter.
Here is a more detailed description of how the HunterLab UltraScan PRO, UltraScan VIS and ColorQuest XE meet the requirements of Section 8.
- For either a network or local PC installation, the person installing EasyMatch QC software must be a System Administrator for the PC, Continue reading
In industrial colorimetry of QA non-luminous materials, assumptions are made that light reflected from or transmitted through a surface is relatively uniform, with only diffuse and specular components. To promote inter-instrument agreement, the CIE geometries for collecting the reflected or transmitted signal of non-luminous materials are standardized into directional and diffuse sphere types.
BRDF measurement serves as more of a research tool when you want to precisely quantify the pattern of light reflecting from a sample surface, or the pattern of light being transmitted through a clear material. Typical materials would be coated surfaces, plastics, films and metals.
Another major application area for BRDF measurement is quantifying the illumination pattern from self luminous light sources such as LEDs and HID lamps; and luminaires such as automotive displays, and architectural lighting.
HunterLab does not make BRDF/BSDF equipment but here are some further resources for equipment and measurement services: