Adobe 13101332 - Photoshop - Mac User Manual page 150

Adobe Photoshop Help
Using Help | Contents
4 For Method, select an option:
Relative to change the existing amount of cyan, magenta, yellow, or black by its
•
percentage of the total. For example, if you start with a pixel that is 50% magenta and
add 10%, 5% is added to the magenta (10% of 50% = 5%) for a total of 55% magenta.
(This option cannot adjust pure specular white, which contains no color components.)
Absolute to adjust the color in absolute values. For example, if you start with a pixel that
•
is 50% magenta and add 10%, the magenta ink is set to a total of 60%.
Note: The adjustment is based on how close a color is to one of the options in the Colors
menu. For example, 50% magenta is midway between white and pure magenta and will
receive a proportionate mix of corrections defined for the two colors.
5 Drag the sliders to increase or decrease the components in the selected color.
Making quick overall adjustments to an image
The Brightness/Contrast, Auto Levels, Auto Contrast, Variations, and Auto Color
(Photoshop) commands change colors or tonal values in an image but are not as precise
or flexible as the high-end color adjustment tools. They provide a quick and simple way to
make overall adjustments.
Using the Brightness/Contrast command
The Brightness/Contrast command lets you make simple adjustments to the tonal range
of an image. Unlike Curves and Levels, this command makes the same adjustment to every
pixel in the image. The Brightness/Contrast command does not work with individual
channels and is not recommended for high-end output, because it can result in a loss of
detail in the image.
To use the Brightness/Contrast command:
1 Open the Brightness/Contrast dialog box. (See
page 132.)
2 Drag the sliders to adjust the brightness and contrast.
Dragging to the left decreases the level and to the right increases it. The number at the
right of each slider value displays the brightness or contrast value. Values can range
from –100 to +100.
Using the Auto Levels command
The Auto Levels command moves the Levels sliders automatically to set highlights and
shadows. It defines the lightest and darkest pixels in each color channel as white and black
and then redistributes intermediate pixel values proportionately. Because Auto Levels
adjusts each color channel individually, it may remove or introduce color casts.
By default, this feature clips the white and black pixels by 0.5%—that is, it ignores the first
0.5% of either extreme when identifying the lightest and darkest pixels in the image. This
ensures that white and black values are based on representative rather than extreme pixel
values.
Auto Levels gives good results when an image with an average distribution of pixel values
needs a simple contrast adjustment or when an image has an overall color cast. However,
adjusting the Levels or Curves (Photoshop) controls manually is more precise.
Using Help | Contents
| Index
| Index
Making Color and Tonal Adjustments
"Making color adjustments" on
Back 150
Back 150