172 PART 3 HOW THE DIGITAL DARKROOM WORKS
How to Change a Red Rose to Blue
One of the most magical tricks of the digital darkroom is the ability to take a
real-world object and give it a new color. We like red and yellow roses, but
without too much effort, we can turn several of them blue. The thing that
makes the change convincing is that the original shading is retained.
Highlights are still highlighted and dark spots are still dark—they’re just
a new color. (Notice, too, that the yellow roses turned out to be a lighter
shade of blue than the red roses.)
How this is done might not be obvious. If we took a
paintbrush in normal painting mode and painted a rose
blue, it would end up as a solid blob of color, without
shadings or edges. And, roses that started out red and
yellow would both end up the same blob of blue.1
In place of a normal
painting mode, the
image editing software
offers a special color-
blending mode. It pre-
serves the gray levels of
the original colors while
blending in the hue and
saturation of the new
color.2