Rooftop Blue

Blue hour is short and the camera usually misses it, landing either on a sky that is already black or on an auto white balance correction that removes the blue entirely.

Rooftop Blue restores it without turning the whole frame cold. Blue lifts strongly in the shadows and midtones and runs to full in the highlights, while red and green are held almost flat, so street lights and lit windows stay warm against it.

The contrast move is small on purpose. At this hour the difference between sky and building is already narrow, and pushing it apart is what makes a blue hour frame look composited.