› ›photoshop user› february 2016046
©Adobe Stock/msdnvThat’s fine to describe content, but instructions are a
bit more challenging. Instructions in this case are math-
ematical functions, which take in information, do some
math to it, and return a result. The math that a function
performs is directed and manipulated by variables. If this
sounds complicated or boring, just hang in there; it’ll make
sense soon!
Let’s put all of this in terms with which we’re familiar.
Functions in Photoshop are things such as adjustment layers,
transparency, and blending modes. Variables is another word
for content, so any image you have on a layer affects how
the function behaves, usually by getting combined with the
content from lower layers.
The simplest example would be two layers. The bottom
layer could be a photograph, and the top layer might be
some text. On the top text layer, the function says, “Any-
where that’s not covered up by text, show the content from
below; otherwise, show the text.” The variables are the pho-
tograph and the text. When you combine them, the result is
exactly what you’d expect: text over a photo.Just so we’re all on the same page, you can think of layers
as containers that stack on top of each other. Each container
(layer) holds information that’s split into two general parts:
content and instructions. Content is stuff you can actually
see in the layer—pieces of your image. Instructions do some-
thing with content to change it, usually by looking at content
from lower layers.
The classic way of
looking at layers is
like a stack of trans-
parencies or glass;
as you look down
on the stack, you
see the composite
of all the individual
contributions. This
painting is made up
of several layers that
combine to give you
what you see on
Photoshop’s canvas.SCOTT VALENTINEPhotoshop Proving Ground
layers, part 1: opacity
HOW TO ››So you know about layers, right? They’re the building blocks of pretty much everything you can do in Photoshop,
from organization to detail work. It’s a pretty basic idea, and it’s probably one of the first things you learned
about in the world’s most popular digital image-editing application. Rather than try and hash over things you
already know, I’d like to present some ways of thinking about layers that should help your understanding of
what layers can really do for you.