Colourise night photos in 4 steps!

1. Duplicate and invert colours

Open your night photo and duplicate it, before inverting the colours. Set the blend mode to Colour, selectCreate a New Adjustment Layer and choose the Channel Mixer. In the following dialog box, configure the Red Output Channel to Blue: +100; the Blue Channel to Red:+100 and the Green Channel to Green:+90.

2. Play with colours

Apply Colour Balance (Cmd/Ctrl+B) and for Shadows use Red:-10, Blue: +10 and Green: 0. For Highlights set Red: -10, Green: +10 and Blue: +10. For Midtones set Red: +10, Green: -10 and Blue: +10. Add a Hue/Saturation layer and up the Red, the Magenta, the Saturation and the Lightness slightly, and boost the Vibrancy.

3. Duplicate and merge layers

Select all your adjustment layers, as well as the inverted coloured layers, and duplicate them. Now select all these duplicated layers and merge them (Cmd/Ctrl+E). From here on, we’ll be using the merged layer.

4. Drama and filter

To finish, duplicate the merged layer and but lock the original layer. Apply a High Pass filter with a 10-pixel Radius, then change the the layer to Overlay blend mode with 100% Opacity. Now merge these two layers.