Measurement geometry is part of the result. A d/8 integrating-sphere instrument, a 45/0 instrument and a transmission setup illuminate and view the sample differently. They should not be expected to agree numerically on every plastic surface.
d/8 geometry
Diffuse illumination with 8-degree viewing is widely used for plastics because it averages illumination direction and can provide SCI and SCE conditions. SCI is valuable when the aim is material color with reduced surface influence; SCE includes more of the visual effect of gloss. Integrating-sphere geometry is also central to many transmission and haze methods in benchtop systems.
45/0 geometry
A 45/0 arrangement illuminates at 45 degrees and views near the surface normal, excluding mirror-like specular reflection by geometry. It can correlate well with visual appearance for suitable flat samples, but can be more sensitive to texture direction and sample presentation. Keep orientation fixed.
Transmission geometry
Use transmission when the requirement concerns light passing through clear or translucent film, sheet or plaques. Specify total or regular transmission as required, control specimen position and path length, and measure haze separately when scattering matters.
Decision checklist
- Opaque, variable-gloss material control: assess d/8 SCI/SCE.
- Appearance-led flat surface comparison: assess the nominated 45/0 or SCE method.
- Clear or translucent transmitted color: use a defined transmission setup.
- Small, curved or textured parts: confirm aperture, port coverage and fixture repeatability.
- Supplier network: standardise geometry and settings before setting shared tolerances.
The SD-300, SD-500 and SD-700 UV use d/8 reflectance geometry. The SD-800B and SD-900B add benchtop reflectance, transmission and haze capability. Verify the exact method against your sample. Read d/8 vs 45/0 and the plastics hub.
Last reviewed 21/09/2026 · Level: Intermediate
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