432
Portable shadows
W
E OFTEN WORK WITH CUTOUT
objects. But sometimes, an object will
have been photographed with a particularly fine
shadow. And why should we go to the trouble
of painting our own in, when we can work with
the real thing?
Here, we’ll look at a couple of techniques
for extracting a shadow from its background.
First we’ll see the simplest method, which
works well when we’re creating montages in
Photoshop.
But frequently, we need to prepare cutout
objects for other applications – InDesign or
Quark XPress, for instance – or to export as a
PNG file with transparency for incorporation
into a web design. In these cases, we need to
treat the shadow in a rather different way. But
there is still a straightforward solution that
produces a shadow with true transparency.
1
The first step is to duplicate the layer, and then cut out the
object from both the background and the shadow. This
royalty-free image comes with a clipping path, so it’s an easy
job; otherwise, it’s not hard to use the Magic Wand to select
the white and so extract the umbrella from it.
You should now have two layers in your document: the
cutout and the original. I’ve added a third layer, filled with
color, so that we can see what’s going on with greater clarity. I
recommend you do the same.
4
Select All and
Copy the original
image, and make a
new Channel in the
Channels panel. Paste
into here. Go back to
the RGB composite, and
load the channel as a
selection (CO6
LA6).
14
Advanced techniques
SHORTCUTS
MAC WIN BOTH
433
HOT TIP
In order for this
technique to work,
the background
has to be truly
white. In the case
of photo library
cutouts, you
can assume this
to be the case;
if you’re using
images you’ve
photographed
yourself, you’ll
need to turn it
white. To do this,
use the white
point eyedropper
sampler in either
the Levels or the
Curves dialog –
see page 112 for
how to do this.
5
Because selections stored as channels use white as the
selected color and black as the deselected color, you’ll
need to inverse the selection (CSi LSi) so
that the black part of the image is selected.
Next, make a new layer beneath the cutout umbrella layer.
Use d to set the foreground/background colors to black
and white, and then OB AB to fill the
selection with black.
6
When we reveal the cutout umbrella again, this is the
result: a truly transparent shadow that we can take
anywhere. To make a flattened PNG or TIFF file, you can merge
the umbrella with its shadow and the transparency of the
shadow will be retained.
3
So far, so good. We can use the two layers chained
together in our Photoshop documents to form a realistic
shadow that travels with the umbrella on top.
But when we hide that green background layer, the white
returns. Even though the shadow layer mode is set to Multiply,
with no background it just shows up as white; the same would
be the case when we export the file as a TIFF or PNG file with
transparency, for use in other applications.
2
Double-click
the original
background’s thumbnail
to make it into a regular
layer. When you change
the mode from Normal
to Multiply, it duly
shades the background
– and the cutout version
above remains solid.
How to Cheat in Photoshop CC
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