To the left is
a list of the Layer Style dialog box panels. Clicking on Blending
Options opens the panel shown. To the right are the standard
buttons and the Layer Style preview button. The middle section
contains the options themselves. In the General Blending section,
you'll see the Blend Mode and the Opacity slider. Changes made here
are immediately reflected in the Layers palette, and changes made
to blending mode and opacity in the Layers palette are shown here.
The Advanced Blending section holds some incredibly powerful
tools. Fill Opacity: This slider allows you to reduce the
opacity of the content of a layer without reducing the opacity of
effects applied to the layer. Drop shadows, bevels, and several
other effects retain the layer's general opacity (set in General
Blending or the Layers palette). 
In the Layers
palette, you'll see that the heart shape (at the top of the layers
palette) is actually a shape layer with effects applied. If no
effects were applied and the blending options were set to the
defaults, a larger, flat, boring red heart would appear. However, a
stroke has been applied, as well as a bevel and a drop shadow.
Below, in the Layer Style dialog box, you can see that the Fill
Opacity has been reduced. This affects only the heart's red fill,
not the beveled stroke. (If we wanted the stroke to be transparent
as well, we would use the opacity slider in the general Blending
area or the Layers palette.) Channels: You can choose to
blend all channels, or specific channels. Knockout: The
specified layer will be used to hide the underlying layers. (Sort
of a reverse layer clipping mask.) The choices are None, Shallow,
and Deep. If None is selected, there is no knockout. When you
choose Shallow, the layer's pixels will knock out underlying pixels
of layers in that same layer set. If there is no layer set, the
knockout extends downward in the layers until either it hits a
background layer or reaches transparency. In the following image,
notice that the heart has been moved into Layer Set 1, with the
type layers. With Knockout set to Shallow, the heart knocks out all
of the layers in the set, but only the layers in the set. 
With Knockout
set to Deep, as shown below, the knockout goes all the way to the
Background layer (or, if no background layer, all the way to
transparency). Note, however, that Set 1's blending mode is Pass
Through in the Layer's palette. When the layer set's blending mode
is any other, the knockout stops at the bottom of the layer set,
even when Deep is selected for a specific layer. 
In addition to
layer sets, knockout can be affected by clipping groups. Blend
Interior Effects as Group: When selected, any layer effect that
ranges inside the actual artwork on the layer (Inner Glow, Satin,
Overlay) is blended with the artwork before the artwork is blended
with the rest of the layers. Blend Clipped Layers as
Group: Layers within the selected layer's clipping group (if
any) will be blended together before they are blended with other
layers. Blend If: When Gray is selected, all channels are
blended using each pixel's luminosity or brightness value.
Alternatively, you can choose to blend the color channels
individually. The sliders control what pixels blend, and how much,
between layers. In this figure, the upper layer (golden chains) is
active and the upper slider is set to exclude the lighter pixels on
that layer. Using the Gray option, the lightness values of each
pixel is evaluated. As shown, any pixel on the upper layer with a
brightness of more than 200 will not be blended, and therefore will
be rendered invisible. 
By holding
down the Option/Alt key, we can split the sliders to define
a range of partially-blended pixels. This creates a smoother
blending. 
In addition to
the value shown above for Gray, we could also blend the individual
channels. (This does not affect the slider positions for Gray.) If
we adjust the underlying image to force blue to blend, areas with
blue pixels in the lower layer will show through the upper layer,
as shown here. 
You can even
drag the light and dark sliders past each other to create fantastic
blends. In this example, we achieve the desired effect of "ghostly
golden chains" by reversing the sliders. 
Reversing the
sliders for the heart layer also changes the look of the underlying
pattern in Hippie Haven's final version. 
In Part II of
this exploration of Layer Blending Options, we'll look at some
particularly practical applications.
Previously featured Planet Photoshop articles, including the other Brushes Palette tutorials, are archived under Featured Columns. Special thanks to www.planetphotoshop.com for allowing us to reprint their Photoshop tutorials here at Renderosity. You can e-mail Pete Bauer, the author of this article, at peterbauer@columbus.rr.com.
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