Automatic Contrast Adjustment; Modifying The Gamma Curves; Graphically Altering A Gamma Curve - Nikon Scanners Software Reference Manual

The Gamma Curve Editor Dialog
This tool can be used with any gamma curve, although it is most effective when
used with the Master gamma curve.

Automatic Contrast Adjustment

(Automatic Black Point and White Point Selection)
If you prefer, the Nikon Scanner plug-in is capable of selecting optimal
Monochrome Points for you. The automatic contrast adjustment control in the plug-in
will usually produce excellent results. Simply click the Contrast Adjust button, shown
in Figure 16.25, in the Gamma Curve Editor dialog. The image data within the crop
rectangle is analyzed to produce the Black Point and White Point. The active gamma
curves will automatically be modified.
Figure 16.25 The Contrast Adjust button.

Modifying the Gamma Curves

Modifying the gamma curves is relatively easy, but modifying them correctly is
not. While the effects of altering the Master curve are relatively straightforward, the
relationships between the Red/Cyan, Green/Magenta and Blue/Yellow gamma curves
are far more complex, and the result more difficult to predict.
The gamma curves can be modified manually or automatically. The manual
mode involves selecting and moving points on the gamma curves with the mouse, there-
by graphically reshaping the curve.
A semi-automated technique involves the White Point and Black Point selection,
which was discussed in a previous section. This will simplify the process somewhat. It
is also possible to use control points to assist in correctly adjusting the gamma curves.
As you learned in the preceding section, the automatic contrast adjustment control is a
fully automated technique for selecting the image's Black Point and White Point.

Graphically Altering a Gamma Curve

The individual gamma curves in the gamma curve window can be manually
altered by clicking the mouse at points on the gamma curve and dragging, thus reshap-
ing the curve. The primary gamma curves are accessed by clicking on the appropriate
button in the Gamma Curve Editor dialog:
Macintosh:
Page 152
Chapter 16
Software Reference for Scanners