Above: Original colour image.
.
The secret here is the small details you
incorporate, and studying just how light
is portrayed on film (or disk).

The Method

1). Open the image ‘french_street.jpg’ Once open in your browser,
you can drag the image to your desktop or Photoshop icon, or right
click to open itin Photoshop.
2). I always duplicate any image I work on, just in case. So press
'Co - J' to duplicate it.


Rather than try and add blue to a mainly yellow image, and end up
getting green, it is best to remove the colour by desaturating it.
3). Desaturate this new layer ‘Co - Shift - U’


We can now turn this to a night time blue cast.
4). Go to ‘Image - Adjustments - Colour Balance’ Try
-50 Cyan, and +70 Blue.
Leave the centre slider at zero. Set the Tone balance at
Midtones.



5) Go to 'Image - Adjustments - Brightness & Contrast'
add some contrast and take the brightness down a tad, so that
it looks like the example (top). Night usualy has more contrast
than daylight. Try -20 for Brightness and +10 for Contrast.



6). Create a new layer; 'Co - Shift - N', or click the new layer
icon at the bottom of the Layers palette.



7). Select your colour swatch on the 'Tool Bar' and type in
FDC20F. This commits the new colour as your Foreground colour.


8).Fill this layer by 'Option/Alt - Delete/Backspace'

What we are going to do now is cut out some window
frames on the blue layer using the Lasso (L) and Eraser
tools (E). If you turn off the yellow layer icon, you
will see just the holes we create in the blue layer.
It is up to you which windows are coloured.

9). Choose the Lasoo Tool (L) and trace the shape of the
glass area of a window. You will need to feather this
selection so that it is not a hard edge. Go 'Select - Feather'
and choose a feather of '0.25' or '0.50' depending on how
much glow you want around your window.




Do this to all the windows where you want to see lights.

10). To give a more lifelike look to your windows, you can
cutout (Co - X) the window frames and paste (Co - V)
them back again onto a new layer (below). You can then
adjust the layer opacity to say 50 - 60% to give the illusion
of a curtain or blind over the window. Often when you look at a
window at night it is very uneven, items inside the room
tend to give off different degrees of reflection etc. It is more
realistic to add things like this in your composition.

 
It is up to you how detailed you wish to make this.

Next we are going to ad the night sky.
11). Select your Magic Wand (W), set the Tolerance to 20.
and with your Shift key held down, hit the sky a number of
times until it is all selected. Don't worry about losing the
power lines as we will add these later.



12). Go 'Select - Feather - 2', then 'Select - Modify -
Expand - 2'. This will pull the selection into the building
by 2 pixels, thus removing any halo.



13). Click the Foreground colour in the Tool Bar, and type
in 143467 to get a deep blue. Click 'X' to get your background
colour, click this and choose white (FFFFFF). Select the
Gradient Tool 'G' from the Tool Bar and drag from the bottom
of the selected sky, to the top of the picture. When you let
go it will fill with a gradient. If the colours are the wrong way
around, drag from top to bottom.



14). Now to the Moon! Create a new Layer 'Shift Co - N' and select
the Brush Tool 'B' and select 100 for brush size (use the Squigly
Brackets to change the brush size up and down). Click once to make
a circle somewhere near the top of frame, half over the building and
sky. Change the Opacity to 40%.


15). Now a new layer again 'Shift Co - N'. This time select a brush size
of 20 and make another moon. Leave this at 100% opacity. Now
in the Layers Palette, link these two moons and then 'Merge Linked'



16). Next with your Lasoo Tool (L) cut the side covering the building,
then 'Select - Feather - 1' to give a soft trasnition to the cut.
Now 'Co - X' to cut this away.


You now have a moon giving a highlight to the cobbled stones.

You can add other elements, such as car and street lights in the
same way as we did with the moon. A 20% over-spill plus 100%
centre intense light. If you wish to have different coloured lights
in the windows, simply make a new layer and fill it with a new
colour (in a selected area only).

One piece of good house-keeping advice here is to name your
layers. With lots of small bits of information in your layers, you
can easily get confused and waste time. Just double click the
name field, and start typing a new name.


That's it, good luck!