129WORkIng WITH LAyERS
Figure 5-1.eveRY Image begins life as a few channels
of data—most commonly, one each for red, green,
and blue—fused into a single pane of pixels (see
Figure 5-1). Whether the image comes from the
least expensive digital camera or a professional-
level drum scanner, it exists entirely on one layer.
One and only one full-color value exists for each
and every pixel, and there is no such thing as trans-
parency. Such an image is said to be flat. But add
images (like the extra arms in the figure) and you add
layers. Each layer serves as an independent image that
you can stack, transform, or blend with other layers.
An image that contains two or more layers is called a
layered composition. There’s no need to wait until a
certain point in the editing cycle to build such a com-
position—you can add layers any old time you like,
as we have several times in previous lessons. But lay-
ers can do more than just add manipulatable imag-
ery your composition. They give you infinite ways
to control how those image components work to-
gether to create the final appearance of your artwork.
The Benefits and Penalties of Layers
Photoshop’s reliance on layers makes for an exceedingly flexible
(if sometimes confusing) work environment. As long as an image
remains on a layer, you can move or edit it independently of other
layers in the composition. Moreover, you can create relationships
between neighboring layers using a wide variety of blending options,
adjustments, and masks, all of which work without changing the
contents of the layers in the slightest.