PSU_February_2016_PDF

PHOTOSHOP PROVING GROUND › ›
content that already has lower Opacity, but Fill can’t add back
Opacity to content.
Blend If: The third kind of layer alpha, found in the Advanced
Blending section of the Layer Style dialog, is called Blend If. This
alpha is only applied to specific kinds of content based on the
brightness value (either gray or individual color channels). Like
Fill, it only considers actual content; layer styles are ignored.
Blend If also has a trick up its sleeve. It uses a comparison
function (the “if” part). Blend If can use the current layer information
(content and instructions combined), or it can use the
output from a lower layer. In plain language, it says to “blend
this layer’s content with whatever is below if some criteria are
met.” The criteria are the brightness values of either layer.
When using Blend If for This Layer, layer styles aren’t
affected—it behaves like a selective Fill Opacity. But when
using Underlying Layer, layer styles are affected.
Mask: There are two more features to talk about that concern
layers and transparency: clipping and masks. Remember
above when I said alpha instructions are actually channels?
Well, here’s where that information starts to make sense.
A mask is really an alpha channel attached to a specific layer
(or group of layers). An alpha channel is a grayscale image
that’s applied to another image and provides instructions
about what’s transparent and what’s not. In the case of
masks, Photo shop treats white as opaque, and black as transparent.
This is mostly independent of other alpha instructions,
and gets added on top of everything else. That means you
still have access to Content Opacity, Layer Opacity, Fill, and
Blend If, and then the layer mask gets added after all of that.
Clipping: Clipping refers to using the content of one layer
as a mask for another. A clipped layer has content and is
above a target layer with content. The clipped layer’s content
only shows up where the target layer content exists. Let’s go
back to our first example and switch the order of the text
and image layers. The text is now obscured. But if we clip
(Option-Command-G [PC: Alt-Ctrl-G]) the image layer to the
text (target) layer, the image content now fills the text.
Next issue, we’ll tackle blending modes and adjustment layers
in terms of how they behave in a stack. It’s gonna get geeky
in here! ■
› › photoshop user › february 2016
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