Treadwell said:

I read somewhere Muren saying that the lasers and lightsabers (some? all?) were subcontracted and they did not get isolated elements back.

As for the two strips of film thing, not necessarily. One exposure with it overexposed so you get the white core, then another exposure on the same frame with the red line lit normally but the camera out of focus.

Thanks, dunno why I didn't think about the possibility of the animation being shot with multiple passes on the same piece of film. That's more likely the way it was done.

Still, the elements could have been adjusted during the recomposites, in a way that made the cores much more visible than they ended up being in the original optical composites (due to grain buildup, color shifts, what-have-you).