Adjusting The Preview Image; Setting Control Points On The Gamma Curves - Nikon Scanners Software Reference Manual

The Gamma Curve Editor Dialog
Histogram
of Preview
Image
Figure 16.18 The histogram of a preview image.
The histogram's horizontal axis represents the pixel intensity, the high density
(darker) values appearing on the left and the low density (lighter) values on the right.
The vertical axis represents a scaled version of the number of occurrences of each pixel
value. The histogram therefore represents a graphical view of the brightness of an
image.

Adjusting the Preview Image

In order to modify the gamma curves accurately and effectively, it is necessary to
understand the nature of the film being scanned. It is possible with the Nikon Scanner
plug-in to perform gradation correction of the image data in the preview window. This
involves setting control points on the gamma curves, selecting the white point and black
point, and performing automatic contrast adjustment.

Setting Control Points on the Gamma Curves

In Figure 16.20, a control point is seen superimposed on the Master gamma
curve. This control point provides a means to relate densities in the preview window to
a point on the Master gamma curve. All pixels in the preview window have colors that
correspond to points on the Master gamma curve. By clicking the Marker button in the
Gamma Curve Editor dialog, shown in Figure 16.19, then placing the mouse over the
preview image, an arrow cursor will appear.
Figure 16.19 The gamma curve Marker button – Macintosh and Windows.
As you move the cursor across the preview image, a temporary marker is displayed
on the active gamma curve and the R,G,B component values of the pixels are displayed
Page 148
Pixel Intensity
Chapter 16
Software Reference for Scanners