Sometimes, a plot theme is explored in several films.
One such theme is “data mining,” for want of a better term.
To satisfy his personal curiosity, the protagonist deeply explores a previously gathered record of an event using his professional techniques, and makes an important discovery. Watching the professional protagonist going about his task for personal reasons is quite interesting.
“Blowup” (1966): Photography. He blows up photographs and explores details in the background.
“The Conversation” (1974) Audio. He uses various audiotape editing techniques.
“Blow Out” (1981) Both photography and audio. He synchronizes a sequence of magazine photographs with his own audio.