Keep illumination and viewing arrangement fixed while comparing two observers’ descriptions. This is a discussion worksheet, not a vision test, calibrated metamer pair or diagnosis.
| Condition | Observer 1 | Observer 2 |
|---|---|---|
| Same two materials, same light, first look | Match / difference / uncertain | Match / difference / uncertain |
| Repeat under the original arrangement | Record again | Record again |
| Change illumination; keep other details comparable | Record separately | Record separately |
Agreement under one condition does not establish identical reflectance spectra. Disagreement can have several causes, including viewing differences, gloss, adaptation, and differences among observers. This casual comparison cannot isolate observer metamerism. A reproducible measurement requires specified geometry, illumination and an observer model.
If both people see the same result, record that too. Do not search for a disagreement merely to fit a story.
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