Color Instrumentation

In industry, there are two classes of instruments used to measure color: 45/0 and sphere geometry.

Control color as you see it
The 45/0 geometry uses 45° circumferential illumination and 0° viewing perpendicular to the sample plane.
The circumferential illumination is essential to achieve repeatable measurement results on directional and structured surfaces.

The 45/0 geometry simulates the normal condition used for color evaluation. For example, when we read a glossy magazine we position it to avoid the gloss from coming into our eye.

A high gloss sample with the same pigmentation is visually judged darker by the eye when compared to a matte or structured sample.

This is exactly what a 45/0 instrument measures:
Differences in gloss / texture -> Color differences
On the automotive interior plaque, you will get a difference between the two structured sides: ΔE* = 3

Applications where it is necessary to have the agreement with the visual assessment are:
• Batch to batch comparison in production
• Assembly of multi-component products using different materials

A sphere instrument may be operated under two different measurement conditions:
specular included (spin) or specular excluded (spex)
In the “spin” mode, the total reflected light is measured:
Diffuse reflection (color) + direct reflection (gloss)
Color is measured independent of the sample’s gloss or surface texture.

Differences in gloss / texture -> Color differences

On the automotive interior plaque, you will get no difference between the two structured sides: DE* = 0

Applications for measurements taken in “spin” mode:
• Color strength depending on dispersion time
• Weathering and temperature influence on color
• Color matching

In the “spex” mode, a gloss trap is used to capture the directly reflected light (gloss). This configuration simulates the 45/0 geometry. In case of medium to low gloss samples, deviations will occur between the 45/0 and the sphere spex configuration as the gloss trap does not completely exclude the specular component.

Summary

Only measurements taken under the same conditions can be compared. Therefore, it is necessary to note the following information in a color measurement report:
• Color instrument (geometry)
• Illuminant / observer
• Color system
• Sample preparation

BYK-Gardner offers a complete line of benchtop and portable spectrophotometers for color measurement.