General Color Information and History
Visual Color Assessment:
Visual Color Assessment requires a controlled and repeatable light source. Light sources or illumination should be chosen to match your customer's requirements. Colour acuity and colour comparisson can vary by simply varying the light source. Eyes can be fooled easily if conditions vary or are illuminated by poor standard store purchased bulbs. Color can and will appear different under different light sources (fluorescence, sun, cloudy afternoon, morning, tungsten, etc). For this reason, Macbeth created lightbooths that are now used worldwide in all industries.
Lightbooths for Visual Color:
Iindustry has standardized on lightbooths to view color visually. Macbeth has become the world renowned innovator and manufacturer of the famous Spectralight series and the Judge series.
Eye Vision Color Tests:
Once the lighting is controlled, we must determine if the person responsible for color determination or color expert has the visual acuity required to discern between colors. Thus Macbeth and Munsell carefully created the Farnsworth 100 Hue test. Imbotec Group will perform these and other tests to all your personnel involved in the critical color arena.
Call us to determine which test is appropriate at 1-866-IMBOTEC (462-6832)
Color and Appearance Measurement Instrumentation:
Instruments were developed to early eliminate human judgment and to reduce internal color discussions and eliminate arguments.
Colorimeters were first developed that use 3 filters to determine the lightness-darkness “L”, red-green ”a*”, and yellow-blue “b”. Colorimeters are usually lower cost and not as critical as spectrophotometers. Imbotec carries a low cost line of colorimeters for simple applications called the PS series.
Spectrophotometers measure color by analayzing the amount of light at specific wavelengths this determining color accurately. Spectrophotometers and colorimeters from some other companies are now equal in price to the more accurate, repeatable spectrophotometers. X-Rite spectrophotometers measure the visual spectrum from 360 to 740 nanometers at each 10 nanometers. They can display the various reflectances at each wavelength and create digital color by presenting color in three values. X-Rite spectrophotometers are available in a range of sizes and configurations depending on the application and your requirements. We provide our Ontario customeres with a choice of three models of handheld spectrophotometers to several benchtop spectrophotometers. If you are unsure and want to discuss your application call us at 1.866.IMBOTEC.
Low Cost Color Readers and Colorimeters:
For relatively easy applications we also carry the PS Series of color measurement devices introduced to make color differentiation affordable to all. Our LED powered colorimeters come with or without software and are available for a wide range of applications to compare colors or even to match a colors to commercially available paints from your local hardware store at a low cost. These colorimeters display color in RGB and optionaly with software in L*a*b*.
This color space presents you with values from 0 to 255 units in each direction of the three dimensions : Red, Green, and Blue. White is 255,255,255. Black is 0,0,0. All other colors fall in between as a mixture of all three. Values increase proportionately, the more saturated the color is.
The most commonly used color space is based on human perception of color; the three color receptors (red, green and blue) in the eye. This results in three sets of signals being sent to the brain: light or dark, red or green, and yellow or blue. They are opposing in that one receives a red signal or a green one, but not both. This opponent type color space is derived mathematically from the CIE values or CIELab, referred to as L*, a*, b*.
L* is a measure of lightness of an object, and ranges from 0 (black) to 100 (white).
a* is a measure of redness (positive a) or greenness (negative a).
b* is a measure of yellowness (positive b) or blueness (negative b).
The coordinates a and b approach zero for neutral colors (white, grays and black). The higher the values for a* and b*, the more saturated the color is.
The system is the same as the CIELab color space, except that it describes the location of a color in space by use of polar coordinates, rather than rectangular coordinates.
L is a measure of lightness of an object, ranging from 0 (black) to 100 (white)
C is a measure of chroma (saturation), and represents the distance from the neutral axis.
h is a measure of hue and is represented as an angle ranging from 0° to 360°.
Angles that range from 0° to 90° are reds, oranges and yellows. 90° to 180° are yellows, yellow-greens and greens. 180° to 270° are greens, cyans (blue-greens) and blues.
From 270° to 360° are blues, purples, magentas, and return again to reds.
Many other equations exist which are beyond the scope here such as CMC, FMC-II, etc.