A sample can look different under a desk lamp, daylight or a camera flash. A repeatable photo station makes later comparison easier without pretending the photograph is a measurement.
A practical check
Choose a fixed background and note the light source, camera position and whether automatic image adjustments were enabled. Include a label with the specimen ID in the frame. Photograph an unmarked control next to the marked area when that helps show the starting surface.
Keep the decision traceable
When comparing two tests, keep the framing and light similar. Store original files and note any edited copies. If the photos still disagree with what you see in person, record that difference instead of selecting the more flattering image.
What this establishes
The photo documents a particular specimen under particular conditions. It does not establish a material guarantee or predict another supplier lot.
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