Maybe it's the lighting or the angles, but I'm noticing something odd. In the shots from the duel there is the very silver and very obvious "reflector" in the emitter, but there doesn't seem to be one (or not the same one) in any of the other shots. I don't know at what point in the production schedule the duel was filmed, but is possible the reflector was a late addition to the design or part of the "rebuild" that explains the differences in the saber through the film. Or am I just completely off my nut here?
Okay, here is my theory.
I believe that the 'silver' inner emitter cone is the same throughout the entire movie, it's just noticeable in the dual scenes because of the way they were filmed.
I think the reason the inner 'silver' emitter cone stands out so bright was the FX used in ANH.
I'm sure most of us have seen the behind the scenes FX shot where Alec is standing there, he freezes, and a stagehand runs in and trades the Hero Saber (pointed at camera) with the bladed stunt version, and then the stagehand runs off camera and Alec resumes his action. The film would then be trimmed to make a 'jump cut' from Hero to bladed removing the stagehand.
As most of you know, in ANH originally the glowing lightsaber blades were filmed as an in-camera effect. The camera shot through a half-silvered mirror, meaning that the camera looked through the mirror at the scene and the mirror was 'invisible' to the viewer. An outside light source was pointed at the reflective side of the mirror off-camera (the mirror was at a 45 degree angle) so there was an extra bright light being shot toward the lightsaber illuminating the reflective material on the blade.
With this set-up no matter how the camera moved the mirror and light was always pointed at the lightsaber blade.
I've got to wonder if the entire dual scene was filmed through the mirror to keep the look and lighting consistent from one scene to the next. Thus, when the lightsaber emitter is pointed anywhere toward the camera it has extra light above and beyond other shots in the entire movie.
That one behind the scenes shot alone with the stagehand would indicate that at least in that scene the mirror and light effect was used, and that is the main shot that shows the bright silver emitter inner cone.
Am I crazy ?