The last time I saw it in 70mm was in 1991, my recollection is that the death star battle had very black space with no garbage mattes (and I was really looking for them after gorging on the VHS throughout the late 80s). A lot of the space battle shots did look rough in the sense of grain or whatever but not in a way that seemed "wrong" or objectionable. It even seemed like a deliberate thing (though I suppose it wasn't), but it made the models look more real, if that makes sense. I remember ILM doing a space battle for Enemy Mine and my friends and I wondering why it looked much faker than Star Wars, like it looked too clean.