In the color and appearance measurement industry we like to use the phrase “correlate to the visual” when describing measurements. This means that instruments that measure appearance properties should give data that supports what we see with our eyes. More…
When it comes time to buy a spectrophotometer it’s important to buy the right spectrophotometer. Nothing will make you feel worse than buying an instrument and then finding out that it doesn’t meet your customers’ requirements, or doesn’t provide you all of the information you need internally. In many cases you will not have a choice; your customer or supplier, or an ASTM or ISO specification will tell you what you need to buy.
While rarely found in nature, white is the color encountered most often in the human environment. It is the color of neutrality, of cleanliness and freshness. White provides contrast with other colors, and can increase the visibility of a logo or printed text. Conversely, yellow is the color of age, of things that are old and worn and uncared for. That’s why for product manufacturers that make white materials or use white packaging, it’s important to get a consistent color with high whiteness to convey to their customers that sense of freshness, that the product is new and clean.
A well-known, if extremely rough, convention in the world of color measurement says that in CIEL*a*b* or CIEL*C*h space, a dE* value of less than one indicates that two colors are visually indistinguishable to the human eye. The reality is far more complex than this. The limits of visual perception actually differ depending upon which portion of color space is being discussed.
Color instruments and software packages all contain references to CIE standard illuminants and observers. What do these terms mean and how are they used in practical color evaluations? The CIE (from the French Commission Internationale de L’Eclairage), or International Commission on Illumination, is the worldwide authority on how we see and measure color. BYK-Gardner uses many of these standards in its instruments and available software packages. This paper will give some easy to understand explanations of these standards and how they should be used.
The tint strength of a paint batch is probably the single most overlooked quality to check. If the paint is going to be tinted in a store or in the plant, even a small variation in tint strength between one batch and another can result in costly touch-up complaints or wasted gallons due to a mistint.
Gloss is an optical phenomenon caused when evaluating the appearance of a surface. The evaluation of gloss describes the capability of a surface to reflect directed light. A gloss meter measures the specular reflection. The intensity of the reflected light is dependent on the material and the angle of the illumination. In order to obtain a clear differentiation over the complete measurement range from high gloss to matte, 3 geometries (ranges) were defined.
Metamerism is a visual phenomenon which can be caused by a number of different factors. The result is that two samples may look the same under some conditions and different under others.
The most common cause of metamerism is that the pigmentation used to make a match is different than that found in the standard. The spectral curves are different even though the L*a* b* values are the same. The effect of different light sources reflecting off of the different materials results in a visual color difference between the two under some lighting conditions.
In the color industry, there are two classes of instrumentation based on their geometry that are used to measure color: “45/0” and “Sphere”.
45/0 Color Instrument
A 45/0 color instrument is used in situations where we want to measure color the way our eye sees color. Gloss levels influence the way our eye sees color. A high gloss sample appears darker to our eye than a matte gloss sample with the same pigment concentration. A practical use for a 45/0 color instrument is to check color consistency of consumer products when appearance is a deciding factor in a product purchase.
So for a 45/0 color instrument,