PhotoPlus X2 User Guide - Serif

Manipulating Images 69
The composite RGB channel is shown only when all the other channels are
shown. When only a single or pair of single channels is shown the
composite channel will never be shown.
To select specific channels for edit:
1. Select the Channels tab. All channels are switched on and are shown by
default.
2. Click on the channel you want to select—the other channels will be deselected
and hidden automatically. Use Shift-click to include additional channels if
necessary.
3. Apply the adjustment, special effect, painting operation, etc. to the selected
channel(s).
When you switch on a channel it is made visible in isolation by default.
Interpreting histograms
The Histogram tab is used to view the distribution of colours and tones spread
throughout your current selection, selected layer or entire photo (by default). This
gives an opportunity to view and interpret a complete snapshot of the range of
colours and, most importantly, the distribution of pixels that adopt those colours.
The histogram doesn't carry out any adjustments by itself, but it is useful for
evaluating the kinds of image adjustments that may be needed. For example, you
can see at a glance if true "bottom" and "top" (dark and light) values are present. If
not, you may wish to apply a Levels adjustment.
For any channel, the horizontal X axis
represents the range of tones, expressed
as a number between 0 and 255, where 0
represents the pixels of value 0, and 255
represents pixels of value 255 (the values
are called levels). Think of the histogram
as being split into three portions—
Shadows, Midtones, and Highlights.