We’ll make calculations
create the selection mask, choose the Image Adjustments/Calculations
command. This is one of the most complex and least user-friendly
tools in Photoshop. It can be used to mix
pictures or the channels of a singular picture, thereby
creating new effects. The possibilities are countless, from
which selection mask is only one. For this you need to carry
out the modifications shown above.
We have chosen Transparency as Source
1. This option is available only if you carried
out step 2. Source 2 is Blue
here, this is channel blue. This way we are mixing a transparent
channel with a blue one. Transparency channel
in the example is completely transparent, i.e. its value
is zero. The blue channel contains the color information
of the sky blue which we will invert, extract from the selection.
As a result, the blue in the sky appears black in the preview.
We have chosen Color Dodge for blending
mode since this differentiated the area of the sky from
the silhouette of the castle hill. The result can be sophisticated
if you vary the Opacity value. When left
at 100%, the picture will be very rough and spotted with
an inaccurate mask, but the result is much better starting
from 90%. Finally we stopped at 40% where
the black of the sky is clearly distinguishable from the
For the next selections it is essential to set Selection
value in the Result menu.
All this might sound quite complicated at first so I can
only recommend that you experiment with it. The aim is to
achieve the selection silhouette (mask) shown in the next