Sure, it's a tech demo. If you set the brightness on the demo to 7 early on and say "This is dark," you can then turn it down to 5 later and that will seem even darker. The idea is to start at 7, not at 5, because when you have to turn it down to 3 you can't see anything.

The Craster's fight and the wall fight were both at night and looked great. But maybe they should have been a bit brighter so there was more room for the narrative dimming and actually seeing things. This all feels like betting into an empty pot, though, because the darkness of episode 3 isn't even a top-10 season 8 complaint for me.

The problem is that if you've already done a battle scene that's as dark as reasonable, you have a problem when you then want to "go darker".