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.
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:
Scottsdale, AZ 85260 USA
North Sutton, NH 03260 USA
Redmond, WA 98053 USA
KU Leuven, dept ESAT, Technologiecampus Gent (KAHO Sint-Lieven)
Light & Lighting Laboratory
Gebroeders De Smetstraat 1, 9000 Gent (Belgium)
+32 9 265 87 13
FAQ: “Do you sell a depolarizer for my HunterLab sphere instrument? On occasion we test polarized samples and there is definitely a dependence on the orientation of the lens. I was wondering if adding a depolarizer would eliminate this phenomenon?”
HunterLab manufactures bench top instruments with two different geometry types: directional 45/0 (or 0/45) and diffuse sphere instruments, as discussed in a previous blog note. A 45/0 directional instrument illuminates the sample at a 45˚ angle from the sample surface and the detector is located 0˚ in line perpendicular to the sample surface. The inverse, 0˚ illumination and detection at 45˚, can also be used and yields equivalent measurements. The MiniScan EZ and ColorFlex EZ instruments are 45/0 instruments and the LabScan XE is a 0/45 instrument. Continue reading
Can you see a visual difference between the three samples above? Chances are if you can see a difference between samples then HunterLab instruments can measure and quantify these variances. There are several ways to quantify differences with color measurement. You can evaluate dL* da* and db* values to see how samples vary from a standard within the L* a* b* color scale. There are also single number metrics that can be used to quantify color differences. Although dL* da* and db* values define color differences well a single number Pass/Fail measurement that defines a 3 dimensional tolerance can be helpful. Continue reading
Why do the samples above look the same under one lighting condition but different under another? These samples exhibit metamerism, which means they match under some lighting conditions but not others. Continue reading
Olive oil is produced by grinding whole olives and extracting the oil by mechanical or chemical means. Olive oil has a wide variety of applications cosmetics, pharmaceuticals, soaps, but most commonly is used in cooking.
Can HunterLab instruments accurately determine the quality of olive oils quantitatively? Continue reading
This is the final blog note article in our series describing the Visual Observing Situation Model in which we will discuss human observers. Previously we discussed how the illuminants and objects are quantified to help measure color.
In the human eye there are rods that are responsible for low light vision and cones that are responsible for color vision functioning at higher light levels. There are three types of cone sensitivities: red, green, and blue. To effectively quantify how the human eye sees color a standard observer (a table of numbers) must be derived.
To develop the standard observer a set of experiments were run to quantify the ability of the human eye to see color. These experiments had a person looking at a white screen through an aperture having a 2 degree field of view with half of the screen illuminated by a test light. The person then adjusted the amount of 3 primary colored lights on the other half of the screen until they matched the test light color. This process was repeated for all colors across the visual spectrum.
The experiments resulted in a x bar, y bar, and z bar function that became the CIE 1931 2˚ Standard Observer. These functions quantify the red, green, and blue cone sensitivity of the average human observer. After these initial experiments were conducted it was found that the cones are spread beyond the area in the eye they were believed to be concentrated. The experiments were re-done in 1964 resulting in the CIE 1964 10˚ Standard Observer.
These experiments provided a table of numbers that effectively quantifies how the human eye sees color and quantifies the last piece of the Visual Observing Situation model. With all three pieces of information the way color is perceived by human observers can now be quantified.