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.
Since directional instruments only measure in reflectance (specular excluded), samples must be opaque or nearly opaque. The geometry of directional instruments makes them optimal for measuring the appearance of samples; appearance includes both the color of the sample as well as gloss and texture. These instruments tend to “see” color the same way the eye does. For example when a shiny sample is viewed it tends to appear darker and more saturated then a matte sample, even if these samples are equally pigmented. The measurements from the directional instruments will reflect the visual observation.
HunterLab directional instruments are a popular choice for many industries because they provide measurements that correspond to visual changes in sample appearance due to changes in either pigment color or surface texture. For more information about this subject please review our Application Note at AN 1033.00 Color versus Appearance.