Adobe Photoshop CS4 - Manual (Page 162)

155 USING PHOTOSHOP CS4
Color and tonal adjustments
Last updated 1/10/2010
View a specific channel in the histogram
If you chose the Expanded View or All Channels View of the Histogram panel, you can choose a setting from the
Channel menu. Photoshop remembers the channel setting if you switch from either Expanded View or All Channels
View back to Compact View.
• Choose an individual channel to display a histogram of the channel, including color channels, alpha channels, and
spot channels.
• Depending on the color mode of the image, choose RGB, CMYK, or Composite to view a composite histogram of
all the channels.
• If the image is RGB or CMYK, choose Luminosity to display a histogram representing the luminance or intensity
values of the composite channel.
• If the image is RGB or CMYK, choose Colors to display a composite histogram of the individual color channels in
color. This option is the default view for RGB and CMYK images when you first choose Expanded View or All
Channels View.
In the All Channels View, choosing from the Channels menu affects only the topmost histogram in the panel.
View channel histograms in color
❖ From the Histogram panel, do one of the following:
• In the All Channels View, choose Show Channels In Color from the panel menu.
• In Expanded View or All Channels View, choose an individual channel from the Channel menu and choose Show
Channels In Color from the panel menu. If you switch to Compact View, the channel continues to be shown in
color.
• In Expanded View or All Channels View, choose Colors from the Channel menu to show a composite histogram
of the channels in color. If you switch to Compact View, the composite histogram continues to be shown in color.
View histogram statistics
By default, the Histogram panel displays statistics in the Expanded View and All Channels View.
1 Choose Show Statistics from the Histogram panel menu.
2 Do one of the following:
• To view information about a specific pixel value, place the pointer in the histogram.
• To view information about a range of values, drag in the histogram to highlight the range.
The panel displays the following statistical information below the histogram:
Mean Represents the average intensity value.
Std Dev (Standard deviation) Represents how widely intensity values vary.
Median Shows the middle value in the range of intensity values.
Pixels Represents the total number of pixels used to calculate the histogram.
Level Displays the intensity level of the area underneath the pointer.
Count Shows the total number of pixels corresponding to the intensity level underneath the pointer.
Percentile Displays the cumulative number of pixels at or below the level underneath the pointer. This value is
expressed as a percentage of all the pixels in the image, from 0% at the far left to 100% at the far right.