Very interesting pics there Belbucus. Unfortunately I don't know enough about telecine transfers to provide an intelligent response. Though I bet Laserman would love to share his thoughts when he gets back from his hiatus. Looking at those pics, the canyon does definitely look darker. Though to me it looks like those images have a very low tonal range. Whites and blacks are crushed and there isn't much midrage. For example, in the image with the Stormtroopers, the brightness of the sky and sand in the middle of the frame is overblown, and yet the leather pouches on the trooper's shoulder are completely dark. Does that mean the image of the canyon is darker than what was actually seen the the theater that day? Maybe, maybe not.

What I know is that for the 1986 laserdisc release of Star Wars, these scenes shot "day for night" look more like daytime shots, and in 1993 they look like nighttime shots. Were these shots adjusted in 1993 to match the original print or was this another "deliberate creative decision"? I don't know the answer to that question, but here are a couple other things I've noticed that differ in between the JSC and the DC/Faces/GOUT:

SC-DC Comparison

The '93 versions have a different fade out and fade in from the part where 3PO says, "Why I should stick my neck out for you..." to "Thank the Maker!". The fade out beginning at 01:19:28:18 (X0 TC Print time) happens about 30 frames sooner on the SC. Why does this happen? Your guess is as good as mine.

Additionally, in the shot of 3PO being lowered into the oil bath, the lights on the back wall actually change color on the '93 versions, but not on the SC. This is the exact same shot though, so there was obviously some sort of additional color timing done to this shot. It makes one wonder if the color changes to the canyon shots were done after the fact as well - as in these were not present on the original film print.