Placed at the mirror angle relative to the viewing port of a d/8 instrument, it lets the surface reflection escape instead of being counted. With the trap open the instrument reads specular excluded (SCE), which tracks how the color looks; with it closed it reads specular included (SCI), which tracks colorant content regardless of gloss. Mixing SCE and SCI values is a frequent cause of disputes between a mill and a printer.
Their L-star is lower because they measured SCE with the gloss trap open, and ours is SCI.
Also heard as
- specular trap
- specular port
Related terms
Integrating sphere
Hollow sphere lined with a highly reflective matte white that bathes a sample in diffuse light from all directions.
d/0 geometry
Measurement setup with diffuse illumination of the sample and viewing perpendicular to its surface.
Gloss
The mirror-like shine of a paper or print surface, measured as specular reflectance at a defined angle.