Nikon Scanners, Software Reference Manual

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in a text message beneath the gamma curve window. If the mouse is clicked, a control
point is placed on the gamma curve for reference. This is illustrated in Figure 16.20.
Figure 16.20 Setting Markers on the Master gamma curve.
This process can be repeated to place additional control points on the Master
gamma curve for reference. For example, you could select a point in the shadows, in the
midtones, and in the highlights, thus leaving three reference markers on the gamma
curve.
Setting the Black Point
The Black Point represents the darkest point in the image.
The Black Point is typically selected such that all values in the image that are
darker than this point can be ‘mapped,’ or converted to black without disrupting the
quality of the image. For example, suppose that a black area in the image is represented
by a 10 in the scanned data. Values 0–9 would be wasted since no pixel in the image
would have any value lower than 10, unless there are no blacks in the original image. By
setting the Black Point to 10, a re-mapping of the data would occur such that a value of
10 from the scanner would consequently produce a 0.
When the Black Point is selected, the active gamma curve is automatically adjust-
ed to reflect this selection. For example, suppose that the original Master curve was a
diagonal linear 1:1 mapping and the Black Point selected corresponded to the Black
Point in the top graph in Figure 16.21. The resulting Master curve would be changed
as seen in the bottom graph in Figure 16.21.
Corresponding Control Point on
Master Gamma Curve Master Gamma
Curve Selected
Color Components
Arrow Cursor
Marker Tool Selected Pixel Location of Cursor
Software Reference for Scanners Page 149
Chapter 16 The Gamma Curve Editor Dialog