User Guide

105
Chapter 6: Making Color and Tonal
Adjustments
y calibrating your system as described in
Chapter 5, “Reproducing Color
Accurately,” you ensure that the colors
contained in images are displayed accurately on
your monitor. (If you have not calibrated, you may
be making adjustments to an image based on a
false representation of its color.) Once your system
is calibrated correctly, you are ready to adjust the
color and tone of individual images by following
the general steps outlined in this chapter.
Using the Adobe Photoshop
color correction tools
All Adobe Photoshop color correction tools
work essentially the same way: by mapping
existing ranges of pixel values to new ranges
of values. The difference between the tools is
the amount of control you have.
For example, the Brightness/Contrast command
makes the same adjustment to every pixel in the
selection or image—if you increase the brightness
value by 30, 30 is added to the brightness value of
every pixel. On the other hand, two of the color
adjustment tools are particularly useful because of
the control and flexibility they provide. Levels
allows you precise adjustments using three
variables (highlights, shadows, and midtones).
Curves replicates high-end color correction
systems and lets you isolate 16 ranges of pixel
values between pure highlight and pure shadow.
For finer control over color, convert your
artwork to a 16-bit image as described in
“Converting between bit depths” on page 69.
When you finish making color adjustments,
convert it back to an 8-bit image.
Using color adjustment commands
You can use most color adjustment tools in three
ways: applying them to one or more channels, to a
regular layer, or to an adjustment layer. When you
make color adjustments to a channel or a regular
layer, you permanently alter the pixels on that
layer.
With an adjustment layer, your color and tonal
changes reside only within the adjustment layer
and do not alter any pixels. The effect is as if you
were viewing the visible layers through the
adjustment layer above them. This lets you exper-
iment with color and tonal adjustments without
permanently altering pixels in the image.
Adjustment layers are also the only way to affect
multiple layers at once. (See “Using adjustment
layers” on page 281; “Color channels” on page 67;
and Chapter 10, “Using Channels and Masks.”)
B