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Hack 23 Multiple Exposures, Digital Style

If you're looking for the
multiple-exposures setting on your digicam, forget about it. It
probably isn't there, unless you own a Fuji pro SLR
camera or one of a handful of other models with this capability. So,
what's the creative digital photographer to do?

In the film world, multiple exposures are a great way to
create interesting, unexpected visual effects. Traditionally, this
was done either in-camera by exposing one frame of film many times,
or in the darkroom by sandwiching negatives together.

Unfortunately, most digital cameras don't support
multiple exposures. But that doesn't mean it
can't be done. Photoshop, the digital darkroom of
choice for many, comes to the rescue.

There are a couple ways to approach gathering your source material
for Photoshop. You can previsualize the final image
you're after, shoot its parts (layers) with your
digital camera, and then assemble these layers on the computer. Or,
if you just want to experiment, grab a few pictures out of your
existing library, mush them together, and see what happens. Suddenly,
every digital image in your photo library becomes potential fodder
for an interesting photo montage.

2.9.1 Assembling Multiple Images into a Montage

For the first option, we're going to shoot
three images, as illustrated in Figure 2-13.

Figure 2-13. A photo montage

As you shoot, try to imagine each shot layered on top of the next
one, resulting in an interesting image. For each shot,
we're going to underexpose by a factor of 2. Set
your exposure compensation to -2 and take three different shots.
You've now captured three underexposed images that,
when added together, will create one well-exposed image.

Bring these pictures into your computer, start up Photoshop, and open
each one in turn. Copy two of the images and paste them into the
first. You should now have a single image file with three layers. If
you open the Layers palette (WindowLayers),
you'll see your three images in the palette, as
shown in Figure 2-14.

Figure 2-14. Three images in the Layers palette

When doing this type of work in Photoshop, you'll often hear the term layers. This is a powerful feature that enables you to make precise adjustments to aspects (layers) of the overall image. In Photoshop CS, you can view the Layers palette by going to Window and choosing Layers from the drop-down menu.

Once you've finished working with the image, save it as a Photoshop file (.psd) to preserve the layers. This is your master image. Then, you can go back and quickly make subtle changes to each layer. If you want to publish your image or send it to a friend, use the Save As command to convert a copy of the picture to JPEG.

You'll now adjust the blending mode to
Multiply. Click on the layer in the Layers
palette to indicate that you want to work on it. Then, select
Multiply from the drop-down menu (in the Layers palette). In Figure 2-14, Layer 1 is highlighted, with Multiply
selected in the upper left. Photoshop's Multiply
feature takes each layer and adjusts its density and highlight colors
relative to the layer beneath it. This accurately creates the same
effect as traditional film-based multiple exposures.

Because you compensated for exposure when you recorded the pictures,
these three light images should now look like one well-exposed shot,
with the random and interesting effects you get from multiple
exposures. You can also make minor density adjustments by using the
Opacity setting in the upper-right corner of the Layers
palette.

2.9.2 Creating Multiple-Exposure-Like Effects

But what if you don't want to go through the bother
of shooting images with exposure compensation? The second option is
to use your current pictures to experiment with
multiple-exposure-like effects. Open up
any number of images and bring them into one Photoshop document. As
in the previous example, adjust the layers to Multiply. Now, adjust
the opacity of the individual layers until you get an even exposure.
Of course, one of the benefits (and frustrations too, because when do
you stop fiddling?) of Photoshop is that you can adjust to your
heart's delight. If a particular image (layer) is
too dominant, adjust its opacity or delete it altogether.

2.9.3 Working in a Truly Digital Darkroom

Back in the darkroom days, technicians often employed techniques
called burning
and
dodging.
And guess what, Photoshop does too! This means that if you
don't like the density of a certain area of your
image, you can tweak it with these adjustments. Select the part of
the layer you want to emphasize or deemphasize, and use the burn tool
to darken it or the dodge tool to lighten it.

Even though creating multiple images has its roots in film
photography, it's a terrific digital-imaging
technique too. Let your visual imagination run wild.

Hadley Stern