Antonioni's Blow-Up, from 1966, is based on a story by Julio Cortázar, "Las babas del diablo". The film keeps the premise: a photographer enlarges a print and finds something in it. It discards almost everything else the story was doing with its narrator.
As I read it, that narrator is the heart of the thing. The story cares less about what the photograph shows than about who is telling us about it, and how unsteady that teller is. A film can keep a camera and an enlargement easily. It has a much harder time keeping a voice that does not trust itself, so Antonioni kept the image and let the voice go.
I do not think that is a betrayal. It is a different work grown from the same seed. But the fame went almost entirely one way. Plenty of people know the film well and have never heard of the story, or of the Spanish title it carried.
That matters to me because the narrator is the part only prose could do. The adaptation kept everything a camera could carry and left the rest behind, and the rest is what made the story worth adapting.
Have you read the story, and did it change what you saw in the film?