Adjusting Histogram Tone Levels - Canon MultiPASS C635 User Manual

Adjusting Histogram Tone Levels

The Preview window contains a number of useful tools to help you
analyze an image beyond what appears on the screen.
A histogram is a useful tool for viewing how levels of gray are
distributed throughout an image. This feedback is useful regardless of
the condition of your computer monitor and is considerably more
accurate.
Click on the individual color boxes to the left of the histogram to
view that channel's data, or click on the gray box to view the overall
summary data.
Each of the following examples shows the display of the histogram
under certain conditions.
This is a normal, uncorrected scan. Notice the concentration of data in
the dark regions, as indicated by the heavy concentration of data content
in the left of the histogram.
Using ScanTastic's Brightness slider, the histogram shows holes where
image data is missing. This is because the data has been "stretched" to
make the image brighter. This may affect image quality and cause
"posterization", or a blotchy looking image.
6-22 Scanning With the MultiPASS C5500 Chapter 6