After the bank robbery, Vienna and Johnny Guitar are riding along in a buggy drawn by a single horse. While the horse sounds like it is only trotting along, the scenery rushing past the buggy makes it appear the buggy is going at highway speed.
When Johnny has the shootout with Bart in front of the hill-top cabin, in the background we can see Vienna standing on the deck of the cabin, her body all the way to the timber railing. She is in sunlight. Then the view of her goes to a closeup, but now she is standing inside the door opening - in what is obviously a studio shot. This is probably connected to the fact that Joan Crawford insisted on her close-ups only being filmed in the studio, where the lighting could be rigidly controlled. No close-up of her was ever shot while on location.