SPHERE COLOR INSTRUMENTS

	ColorQuest XE Sphere
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A sphere instrument, with the sphere coated white inside, allows you to gather all of the reflected light from the sample to be measured. The light source is usually outside the sphere and designed to illuminate the sample from all directions (diffuse illumination). A set of optics is aimed at the sample through a hold from the other side of the sphere (typically 8 degrees off center). The rest of the instrument design is often the same as a standard 45-degree instrument. Sphere instruments offer the advantage of measuring rough and very shiny surfaces well. When you gather all of the surface light (specular component included) as well as the reflected light, the color measurement is more independent of surface condition. For many color mixing applications in industry, this is a good approach. If you want to measure color with a sphere instrument similar to a 45-degree instrument it can be accomplished by allowing some of the surface light escape from the sphere. This is done by cutting a hole in the back of the sphere that can be covered or opened. Measuring color with the hole open is called specular component excluded.

Sphere instruments are more flexible and give a range of methods to measure a variety of materials. A cut can be made in the instrument behind the sphere and a transmission section added to allow both reflection and transmission color measurements. The disadvantage in sphere instruments are that they are more costly to build; the sphere darkens or yellows with age requiring re coating the sphere with white on a regular basis (costly); and the very flexibility that is an advantage can cause operator errors. Procedures need to be implemented to assure, that the instrument is always set the same way when measuring the same type of materials.