Microtek ScanMaker 5 User's Guide download pdf (Page 136)

6-58 Microtek ScanWizard 5

Tone Curve tool

The Tone Curve tool lets you control the gamma, which measures the intensity

affecting the mid-level grays (midtones) of an image.

Gamma is commonly used to describe the relationship between output density

to the original density across the mid-tones. Adjusting the gamma lets you

change the values of the middle range of gray tones without dramatically

altering the shadows and highlights.

In many ways, the Curve tool gives you the most control for adjusting an

image's values, but beginners may take some time to master its intricacies. The

Curve tool applies to grayscale and color images and is not available for use with

line-art or halftone scan modes.

How to read the curve

The curve shows the relationship of the brightness changes across the middle

pixels between the resulting image and the original.

When you open the Curves dialog box, the line on the graph is diagonal

because the Input and Output values are the same.

The x axis of the graph represents the original brightness values of the pixels,

from 0 to 255, for 8-bit scanners (see the table on next page); the y axis

represents the new brightness values. Clicking on the diagonal line then plots a

point that can be adjusted.

Modified curve with

points moved up

Original curve: Straight

diagonal line

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Microtek ScanMaker 5 User's Guide Page 136