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KELBY ONE.COM[ 51 ]Throughout this article, we’re going to
move around this histogram mountain range
using adjustment layers. This will help us better
comprehend what each slider in the adjustment
layers does to the tonal values, and you’ll be
able to use that to your advantage later when
we create our own looks.
BRIGHTNESS/CONTRAST
We’re going to start with the Brightness/Con-
trast adjustment, as that’s the one that can be
found in most image-processing applications. It
lets you make simple adjustments to the tonal
range of an image.
According to the Adobe Photoshop User
Guide, moving the Brightness slider “to the right
increases tonal values and expands image high-
lights, to the left decreases values and expands
shadows.” So through a complicated algorithm,
the image gets either brighter or darker, mostly
by moving the midtones (the values around the
vertical centerline of the histogram).
On the other hand, the Contrast slider “ex-
pands or shrinks the overall range of tonal
values in the image.” This translates (again,
through a complicated algorithm) to either
making the histogram mountains more promi-
nent and spread out—hence resulting in more
contrast—or reducing the height and width of
the mountain range, making the entire image
flatter with less contrast.
This might all seem a bit complicated, so
let’s see how this looks in practice. Go to
Layer>New Adjustment Layer>Brightness/Con-
trast to create a new Brightness/Contrast ad-
justment layer on top of the Background layer.
Now, while looking at both the histogram and
the image, drag the Brightness slider in the
Properties panel to one side and then the other,
and note the changes on the histogram. When
you move the slider to the right, it moves cer-
tain bumps in the histogram to the right side,
toward the brighter values, making the image
brighter without brightening the darker values.
Moving it to the left results in the opposite:
more bumps move toward the darker values,
and the image becomes darker overall without
darkening the extreme highlights.