User Guide

Operating VRS
VRS User’s Manual
39
Understanding Contrast, Brightness, and Gamma Settings in VRS
What are brightness, contrast, and gamma in VRS? When an image has high
brightness, it seems to give off more light. It is like looking at a drawing under a 45-
watt bulb, then looking at it using a 75-watt bulb. The drawing will seem “brighter”
under the 75-watt bulb. In the same way, moving the Brightness slider up will
increase the amount of light in the image. Moving it down will decrease the amount
of light.
The VRS manual brightness setting ranges from 0 (very dark) to 100 (very bright).
Adjusting the Manual Brightness setting by moving the Brightness slider, by entering
a new value in the Brightness numeric text box, or by clicking within the Brightness-
Contrast custom control causes Auto Brightness to be turned off.
Contrast is the amount of difference between the lightest and darkest areas on an
image. For example, no matter what flash you use, the ratio of light to dark in a
photograph stays the same. When you increase the contrast on a totally black and
white image (binary image), the white parts become whiter and the black parts
become blacker.
A Gamma value is a way to manually “sync up” the image you see on the screen with
what you are supposed to see. In other words, sometimes output devices (monitors,
televisions, etc.) do not produce the same image as the input devices (the scanner, for
example) tell them to produce. In VRS, moving the gamma slider to the right will
remove pixels from the entire image, which will create an overall appearance of
brightening the image. Moving the slider to the left will do the opposite—adding
pixels to make the overall image appear more dark, or dense.
VRS handles this gamma adjustment automatically for you, so even though the
gamma correction slider is available, you will not need it to adjust images. Gamma
should be considered as a scanner calibration and the default value should be
maintained.
Now let us put these image components to use in creating exceptional images.
Divide and Conquer
Every scanned image has two basic parts: the part you want and the part you do not
want. One of the major tasks of any image processing software is to separate these
two entities so that the desired elements are preserved. VRS excels at this task, but
you are probably wondering why. VRS takes advantage of two different technologies
to achieve this—simple thresholding and edge detection.
In simple thresholding, a grayscale image (256 levels of gray) is converted to a binary
image (two levels: black and white). This is done by first setting a threshold level,
which acts like a dividing line. Everything (all the pixels) above that number (level of