Graphic designers build up complex images layer by layer, starting
with the background and gradually adding individual elements and
special effects until the image is complete. Many photographers use a
similar approach when composing an image, viewing the foreground,
the middle distance, and the background as separate zones, be it with
regard to focus, lighting, or formal and color-based composition.
The second phase of digital image creation involves processing the
images you have captured and often entails optimizing individual
image layers separately from one another. For example, a background
that has been deliberately blurred requires much less sharpening than
the main subject, which will usually be portrayed with maximum
contrast. Tonal values, too, often require a layer-based processing approach,
with shadows being treated differently from transitions or
other elements within the frame. Colors can also be processed in separate
zones, with some requiring desaturation while others are intensified.
Such processing steps can also be applied with differing strengths
from zone to zone to enhance the effect of an image and steer the
viewer’s gaze within an image.
However, even if you don’t use layers or zones of focus in your
basic composition, there is a multitude of other reasons to use layer
techniques during image processing, and you will get to know many of
them in the course of this book.