User's Manual

278
ADOBE PHOTOSHOP CS2
User Guide
To view channel histograms in color
❖ From the Histogram palette, do one of the following:
• In the All Channels View, choose Show Channels In Color from the palette menu.
• In Expanded View or All Channels View, choose an individual channel from the Channel menu and choose Show
Channels In Color from the palette 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 thechannelsincolor.Ifyou switch to CompactViewthe compositehistogram continuestobeshown in color.
To view histogram statistics
By default, the Histogram palette displays statistics in the Expanded View and All Channels View.
1 Choose Show Statistics in the Histogram palette 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 palette displays the following statistical information below the histogram:
Mean Represents the average intensity value.
Standard deviation (Std Dev) 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.
Cache Level Showsthe currentimage cacheusedtocreatethe histogram. When thecache levelishigherthan1,the
histogram is displayed faster because it is derived from a representative sampling of pixels in the image (based on the
magnification). The original image is cache level 1. At each level above level 1, four adjacent pixels are averaged to
arrive at a single pixel value. So, each level is half the dimensions (has 1/4 the number of pixels) of the one below.
When Photoshop needs to do a quick approximation, it can use one of the upper levels. Click the Uncached Refresh
button to redraw the histogram using the actual image pixels.
To view the histogram for a multilayered document
1 Choose Expanded View from the Histogram palette menu.
2 Choose a setting from the Source menu. (The Source menu is not available for single-layered documents.)
Entire Image Displays a histogram of the entire image, including all layers.
Selected Layer Displays a histogram of the layer that’s selected in the Layers palette.
Adjustment Composite Displays a histogram of an adjustment layer selected in the Layers palette, including all the
layers below the adjustment layer.