Wait, his "graph" measures a greater gamut of colors in photos from the nineteenth century when they were all B/W? Who's still buying this retvrn hucksterism?
The graph is from a study of objects held in the collection of a museum, not photographs by year they were taken. It says so in this article.
https://lab.sciencemuseum.org.uk/colour-shape-using-computer...
Current photos of old objects. I admit I had the same question based on the caption included in the graph itself, which just says "photos."
> a study of over 7,000 objects in the UK’s Science Museum found that the colors of consumer goods have been steadily neutralized since 1800. Bright, saturated tones have been giving way to gray, beige, and taupe for centuries.