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SIGMA Photo Pro User Guide
36
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Reading the Histogram
To view the Histogram, display the Adjustment Controls Palette on your screen, and open the panel titled
Histogram.
The Histogram graphically displays the distribution of brightness values in your image. There are three
readouts depicted as colored lines which each represent the brightness values of the Red, Green, and Blue
channels. These represent the same RGB values you see individually recorded in the lower right hand
corner of the loupe in the Review Window.
Shadows are represented on the left side of the graph, mid-tones in the center, and highlights on the right
side of the graph. The scale in which these values are measured is between 0 (blackest shadow) and 255
(whitest highlight).
Enabling, disabling and setting values for the Warning Masks
To turn the warning masks on and off click the checkmark box at the bottom of the Histogram panel. You
can set the values in the warning mask to alert you when a shadow or highlight value on one or more of the
channels falls outside of the specified values.
For example, you may discover
that your printer or color lab
cannot produce good shadow
detail when values fall below 8,
and that highlights appear blown
out above the value 240. With
this information, you can set the
warning mask to alert you when
the values exceed these limits. To
set the limits, click on the arrow
buttons below the histogram until
the shadow and highlight values
are set.
Once you have set the values for
the mask, you can manually
adjust the sliders in the
Adjustment Controls Palette until
the warnings are reduced or eliminated. Below is an example of a Review Window with the Warning Mask
enabled. This powerful feature helps you to best use the tonal range for your finished print.
Click the button to
open and close the
Histogram Panel
Click on arrows to set
the shadow and
highlight values for the
warning masks
Turn the warning
masks on and off
by clicking on the
checkmark box