User Guide

Canvas 12 User Guide
Levels dialog box
Use the Levels dialog box to control different aspects of brightness levels.
Channel Choose an individual color channel or the composite channel.
Input Levels Type values in the Input Levels boxes or drag the slider under the
histogram to set the minimum input level, midtone ratio, and maximum
input levels.
Output Levels Type values in the Output Levels boxes or drag the sliders to set the
minimum and maximum output levels.
Histogram The histogram graphs brightness levels for the selected channel.
Auto Click Auto for Canvas to map the darkest values in the selection to black
and the lightest value to white.
Eyedroppers Click the Set White Point eyedropper tool. Click in the image to pick the
values you want to assign to the lightest area in the image. Click the Set
Black Point eyedropper tool. Click in the image to pick the values you
want to assign to the darkest area in the image.
Adjusting brightness curves
You can adjust the tonal range of an image with the Curves command. Unlike the Levels command,
which can set the minimum, maximum, and median values, Curves adjusts the entire range of
values. It lets you map input values to output values according to a line (“curve”) on a graph. Curves
provides the most control over the tonal range of an image.
This command is not available when a paint object in Black & White mode or Indexed mode is
selected.
In the Curves dialog box, brightness values range from 0 (black) to 255 (white), or 0 percent (white)
to 100 percent (black). To switch between these scales, click the grayscale bar under the graph.
A typical setting is a gentle S-curve (or inverted S-curve, depending on the scale you use), which
adds contrast to an image without appearing too harsh.
Curves dialog box
The graph shows how Canvas maps input brightness values to output values. Select Preview to see
the effect on the image.
Channel Choose a channel to adjust.
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