So the sit room is interesting because it isn't a single room.

It is several, which is why all three of your photos look so different. That said, none of them look like the situation room in the west wing so you are correct there. The only room in the sit room that is darker lit is the monitoring room, due to it being filled with TV and computer screens to monitor high priority Intel for the wh by sit room officers. That said the president would likely never be in there.

Fun fact about the last photo from the bin laden raid - Obama didn't want everyone in the wh to know what was happening, so they set up in the "small room" in the sit room, and the photo was taken by his photographer crouched on a tiny desk in the corner.