7
7
A
A
D
D
J
J
U
U
S
S
T
T
I
I
N
N
G
G
I
I
M
M
A
A
G
G
E
E
S
S
7
7
.
.
4
4
U
U
s
s
i
i
n
n
g
g
t
t
h
h
e
e
H
H
i
i
s
s
t
t
o
o
g
g
r
r
a
a
m
m
a
a
n
n
d
d
W
W
a
a
r
r
n
n
i
i
n
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g
g
M
M
a
a
s
s
k
k
s
s
Reading the Histogram
To view the Histogram, display the Adjustment Controls Palette on your screen, and open the panel titled
Histogram.
Click the button to
open and close the
Histogram Panel
Turn the warning
masks on and off
by clicking on the
checkmark box
Click on arrows to set
the shadow and
highlight values for the
warning masks
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.
SIGMA Photo Pro User Guide
32
