Adobe PHOTOSHOP 5.0 User Manual page 126

118 CHAPTER 6
Making Color and Tonal Adjustments
You can also enter values directly into the Input
Levels text boxes.
Original
Resulting histogram
Suppose instead you want to decrease the contrast
in the image. If you drag the Output Levels white
triangle to 220, pixels with brightness values of 255
are remapped to 220, and pixels with lower
brightness values are mapped to corresponding
darker values. This darkens the image, decreasing
the contrast in highlight areas.
You can also enter values directly into the Output
Levels text boxes.
A
A. Decreases shadows B. Decreases highlights
If your image also needs midtone corrections,
4
you can set them now with the Levels dialog box.
Do this before applying the levels changes. (See
"Adjusting the midtones using the Levels sliders"
on page 119.)
Click OK.
5
To view the new histogram, reopen the Levels
6
dialog box. The histogram has been stretched out
to accommodate the new white and black points,
causing gaps in the histogram.
These gaps do not indicate a perceptible problem
in the image unless they are large or accompanied
by a low pixel count.
Setting the highlights and shadows
automatically
The Auto Levels command and Auto buttons in
the Levels and Curves dialog boxes perform
automatically the equivalent of the Levels slider
adjustment: they define the lightest and darkest
pixels in each channel as white and black and
then redistribute the intermediate pixel values
proportionately.
B