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CHAPTER 4
88
Making Color and Tonal Corrections
avoid altering the color balance. You can use the
middle Input slider to change the intensity values
of the middle range of gray tones without dramat-
ically altering the highlights and shadows.
To adjust tonal range using Levels:
1
Do one of the following:
•
Choose Enhance > Brightness/Contrast >
Levels.
•
Create a new Levels adjustment layer, or open an
existing Levels adjustment layer. (See "Using
adjustment layers and fill layers" on page 181.)
2
To adjust values for a specific color channel
(red, green, or blue), choose an option from the
Channel menu.
3
To adjust the shadows and highlights, do one of
the following:
•
Drag the black and white Input Levels sliders to
the edge of the first group of pixels on either end of
the histogram. You can also enter values directly
into the first and third Input Levels text boxes.
•
Drag the black and white Output Levels sliders
to define new shadow and highlight values.
You can also enter values directly in the Output
Levels text boxes.
For example, suppose you want to increase the
contrast in an image with pixels that currently
cover a range of only 0–233. If you drag the Input
Levels white triangle to 233, pixels with intensity
values of 233 and higher (in each channel of the
image) are mapped to 255; pixels with lower
intensity values are mapped to corresponding
lighter values. This remapping lightens the image,
increasing the contrast in highlight areas.
Original
Resulting histogram and image
Suppose instead you want to decrease the contrast
in the image. If you drag the Output Levels white
triangle to 220, pixels with intensity values of 255
are remapped to 220, and pixels with lower
intensity values are mapped to corresponding
darker values. This darkens the image, decreasing
the contrast in highlight areas.
Note: You can click Auto to move the highlight and
shadow sliders automatically to the brightest and
darkest points. This is the same as using the Auto
Levels command and may be adequate for an
average-key image. (See "Using the Auto Levels
command" on page 86.)
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