A Short Guide To Tone Curve Corrections - Minolta DIMAGE Scan Dual III Instruction Manual

D
IMAGE SCAN DUAL III UTILITY

A short guide to tone curve corrections

Image processing is a highly specialized and difficult field that takes years of prac-
tice to master. This basic guide to using tone curves covers a few simple procedures
to improve your pictures. For more about digital-image processing, consult your local
book dealer about self-help guides on this subject.
Bringing out detail in the shadows
This is a simple technique to make a subject hid-
den in the shadows brighter. Unlike the bright-
ness level control (p. 70), this method of correc-
tion will not loose details in the highlight areas of
the image.
With the RGB channel selected, place the
smooth-curve cursor on the center of the curve.
Click and drag the curve up. Look at the displayed
image to judge the result. The adjustment can be
very small and still have a significant impact on
the image. Moving the tone curve down will make
the image darker.
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IMAGE PROCESSING
Increasing image contrast
The contrast of an image can be changed. The
light blue 45° line on the tone-curve graph repre-
sents the original contrast of the image. Making
the angle of the tone curve greater than 45° will
increase the contrast. Making the angle less than
45° will reduce the contrast.
Correcting color
By selecting individual color channels on the tone curve, adjustments to the overall
color of an image can be made. This can be used to eliminate unnatural color casts
or add warmth to a picture.
If the image is too red, green, or
blue, simply drag the correspond-
ing color-channel curve down until
the color appears natural. If the
color cast is predominantly one of
the secondary colors, cyan,
magenta, or yellow, move the
curve of the complementary color
up. For example, if the image is
too yellow, move the blue curve
up, see the color example on page
2. For more on complementary
colors, see page 90 and 91.
With the RGB channel selected,
click on the tone curve near the top
and bottom to add two nodes.
Slightly move the top node up and
the bottom node down. This will
increase the angle of the central
portion of the tone curve and
increase the contrast of the image
without making an overall change
in image brightness.
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