On what viewers know and assume
“If viewers know (or think they know) how the photograph they’re seeing was made...”
Most of the time viewers cannot know how the photograph they’re seeing was made.
Thus the key factor becomes “what viewers think they know” — that is, their assumptions, expectations, and skepticisms.
Viewers’ assumptions have radically reversed in the past 20 years
1. In the 19th and 20th centuries, it was very difficult to doctor a photograph without making it look less believable.
As a result, viewers tended to assume that
“Convincing-looking photos are usually undoctored no matter how remarkable they look.”
2. But in the 21st century, it is very easy to doctor a photograph without making it look less believable.
As a result, in the digital era the public is learning to assume that
“Remarkable-looking photos are usually doctored no matter how convincing they look.”
(“Doctored” unless labeled otherwise, that is, in a setting that viewers trust. That’s why the “Guaranteed TCQ” label was created.)