A glass plate, bright suits and many copies.
NASA’s cameras had a glass Réseau plate pressed against the film, engraved with a grid of small crosses used for measuring distances in photos. [1]
A thin black line on a bright white object can be swamped by light spilling over from the bright area, especially after copying and printing. The cross is still there, just too faint to see in that spot. The best scans often show the faint line. [2]
Checking the exact frame number in the best available scan is the fair test. A crop in a meme may be several generations from the original. [2][3]
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