FAQ: “What is the limit on the standardization in TTRAN. Using the small sample flask, filled with Ultra pure water. If they follow the protocol, they expect to find values (CieLab: 100.0; 0.0; 0.0)?” Continue reading
FAQ: “Do we have to keep the white tile at the reflectance port during transmission readings?” 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.
HCCI – HunterLab Coffee Color Index measures the reflectance of ground coffee products at 640 nm, which is optimal for defining the degree of roast. Continue reading
FAQ: “A client gave me 3 equal size diamonds for color measurement and I have measured them using a reduced sphere exit opening Continue reading
HunterLab instruments measure the color as it relates to the quality of the product. To be able to begin to measure and quantify color we have to know more about why colors appear as they do. As humans we all see and perceive color differently; this is because the human perception of color is a psychophysical response. The visual observing situation model shown above illustrates the three components necessary for the perception of color. Continue reading