A great video on Who Framed Roger Rabbit and bumping the lamp is kaptainkristian's: https://www.youtube.com/watch?v=RWtt3Tmnij4 . Seeing this just the other day inspired me to re-watch the film last night, and I wasn't disappointed: it holds up well.
The classic(al) example I recall from college is that there were a lot of details and general quality in the statues atop the Parthenon that could not possibly have been visible from the ground.
If the studio pushed back against Zemeckis's request, the lamp wouldn't have been bumped, Disney would have saved a massive amount of production time and production cost, and the viewers wouldn't have noticed the difference.
How many awful movies have similar lamp bumping stories that don't get told because the viewers don't care about those movies? It's not the lamp bumping that makes the movie. Don't make extra work for yourself.
Plinkett is saying that my brain noticed that the animation correctly accounted for the movement of the lamp. That is not an argument against not bumping the lamp in the first place.
I'll bet dollars to donuts that Howard the Duck, Waterworld, and every other big budget bomb you can think of has a lamp bumping in it. They were wastes of money in those movies, and if those movies had been successful like Who Framed Roger Rabbit, they still would have been wastes of money.
Lamp bumping telegraphs that the creators took pride in their work. It makes watching a film more rewarding to know you're enjoying something someone wanted you to enjoy, not something that was just thrown together to make money.
I've been watching Deep Space Nine lately and the amount of lamp-bumping in it (especially given that it was a television serial) makes me appreciate it that much more. (My favorite example thus far is the scene when Garak tortured Odo. When Odo returned to liquid form, even the small parts of him that had flaked off were animated as part of the special effect, even though they were barely visible on camera.)
Viewers don't explicitly note the event, but they do become more immersed. The movie wouldn't have been so much of a landmark if they just plonked the animation on top of the live filming with no thought to lighting and environment.
