As for other vader shots that Ady's changing, I'm putting lots of money on this one.
For the longest time, I wondered why they forgot to put a cape on Vader in this shot, as it looks like he's just wearing that tunic underneath.
Wasn't until the blurays that it was 100% clear that it was just that Vader had his hands behind his back. They probably filmed this plate while Prowse was impatiently waiting between takes, and what we get is a very strange, casual Vader stumbling on set.
