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Chapter 12 AFX PlugIns
Histogram
The histogram displays the number of pixels in the channel at values ranging from 0 to 255. This shows
whether the values of pixels are distributed throughout the possible range; if not, you may be able to
improve the quality of the image by remapping the pixels’ values to make better use of the available
range.
Input Black and Input White
The triangle sliders on the first line under the histogram represent the lower and upper ends of the range
of input values included in the remapped output. The middle sliding triangle on the Input slider (top
slider) represents the gamma curve. This curve controls the distribution between the lower and upper
ends of the input values (as set by the left and right sliding triangles on the Input slider).
Moving the Input sliders toward the middle increases the contrast in the image, and moving the Output
sliders in decreases the contrast of the image. Using the Levels effect is different from changing the con-
trast with the Brightness and Contrast effect because the Levels effect can weight changes toward the
highlights or the shadows. You can also adjust the gamma curve with the Levels effect.
Output Black and Output White
The black left and white right sliding triangles under the gradient show the output values to which the
input range is remapped. To change dark—but not black—areas to black, drag the left Input slider to the
right and leave the left Output slider all the way to the left of the Output slider bar. To lighten black areas,
making them gray, drag the left Output slider to the right and leave the left Input slider all the way to the
left. To change light—but not white—areas to white, drag the right Input slider to the left and leave the
right Output slider all the way to the right of the Output slider bar. To darken white areas, making them
light gray, drag the right Output slider to the left and leave the right Input slider all the way to the right.
 Input Min and Input Max -
specify the minimum and maximum input values for the channel.
 Output Min and Output Max -
specify the minimum and maximum output values for the channel.
 Gamma -
specifies the gamma value for the channel.