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[ 55 ]EXPOSURE
The last adjustment we’ll look at is Exposure. It was mainly designed to be used on
32-bit HDR images (this is actual high-dynamic range images, not the tone-mapped
ones). It still works on 16- and 8-bit images, but with less control. In a 32-bit envi-
ronment, its sliders do exactly what they say: The Exposure controls the exposure,
Gamma controls gamma, and the Offset can offset everything but the highlight val-
ues. On a 16- or 8-bit image, it works more like the Levels adjustment with set limits.
It’s better to jump into Photo-
shop and see what the sliders do
both visually and on the histogram.
So go to Layer>New Adjustment
Layer>Exposure. Since most of us
only use images up to 16 bits, let’s
explore what each of the sliders does
to our tonal values.
Usually, Exposure adjusts mostly
the midtones and lower highlights,
and one might think that the first
slider in the Properties panel does the
same, but that’s not the case. If you
start adjusting the slider, you’ll notice
that it shifts the highlights with mini-
mal effect to the extreme shadows. It
can even start creating
gaps on the whites side
of the histogram, which
means that it can darken
the absolute whites in the
image. Not exactly what
one might expect from a
slider called “Exposure,”
so don’t let the name
fool you.Essentially, Curves can achieve
the same results as Levels. The only
difference is that you can add a point
anywhere along the curve and shift
its value in any direction, giving you
immense control.