Operation Manual

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The Tool Chest — Curves
When the cursor is moved over the curve edit display, the
input and output values for the point under the cursor are
shown in the input/output display.
The “Apply” Button
The “Apply” Button
Changes to curves only apply when the button at the top left corner of
the “Curves” palette is checked. When this button is checked, changes
to curves will be refl ected in the image in the active window. The box
can be checked and unchecked for a quick “before-and-after” compari-
son to determine whether changes to settings are having the desired
effect.
Apply button
Input/output display
Step 1—Viewing the Histogram
The fi rst step in adjusting tone levels and
color balance in the “Curves” palette is
to view the histogram displayed in the
background of the curve edit display. The
histogram provides information on what
tones are present in the original image
and in what amounts, information that
is used when setting the black point and white point and
editing curves.
The histogram takes the form of a bar graph. The horizontal
axis shows the tone level (pixel brightness), with shadows to
the left and highlights to the right. The vertical axis gives the
number of pixels of each tone level found in the current crop,
scaled to fi t in the curve edit display (note that the histogram
does not show the position of pixels within the crop).
To view the distribution of tones in the fi nal, output image
after changes to curves, click the
button. Click the but-
ton again to view the input tone distribution.
Sixteen-Bit Images
Sixteen-Bit Images
The histogram uses eight-bit precision, with the result that spikes may
be visible in the histogram when previewing images at a bit-depth of
sixteen bits. Sixteen-bit precision is however used when the image is
scanned.