I'm still playing around with the capture settings - I strongly believe it's better to capture the video correctly in the first place than to apply filters to correct it during post-processing.
With reference to the screenshots I posted in the "official" thread, I think that the brightness (aka "black level") and contrast ("white level") are set pretty close to the ideal. Vader's cloak is black and the roof lights are white. (I should make spot checks to ensure that all the discs are all consistent with each other).
Using the vdub plugin here to analyse the video, it turns out that the colour is slightly over-saturated. Where Artoo wakes up in the sand crawler, his red light is too "hot" and will clip on a TV.
Also I dislike the edge enhancement effect I'm seeing in my screenshots - this isn't caused by the sharpening filter as I first thought, it's present on the source video. Again I'm going to have to look at the capture card drivers, and if there's nothing I can do there then maybe look for a filter to reduce the effect.