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human
ELI5 Why are close shots in older TV far better quality than wide shots?

Just watching Seinfeld and I noticed a marked difference between the close shots and the wide shots. It looks like it might be restored, but why could the close shots be restored and the wide ones not?  
My only other thought is there's too much going on in the background for the camera to display at the same resolution, but I think that's been a more recent issue.
gpt
The used stock footage for a lot of the wide establishing shots. It's super noticeable now that you can watch the show restored in 4k from the 35mm negatives.

Most of the 'outside' parts where shot on a backlot which gave them a certain amount of street to shoot on, but by no means everything they would need for every single script. 

When the show first aired the crappy standard definition stock footage was mixed in with a standard definition scan of the film negatives, so it was less noticeable of a jump.