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3
Input edit boxes
The input values are related to the position of the indicators along the histogram. For example,
if you move the left triangle in from 0 to 30, the input range becomes 30 to 255, and pixels in
the range of 0 to 30 are then set to 0. In a process called mapping, the new range (30 to 255)
is stretched back to become 0 to 255. The image then becomes darker, since all pixels from 0
to 30 are now mapped to black (whereas 0 to 30 before had subtle gradations from black that
lightened gradually). The same principle applies when you move in the right triangle, and the
highlights in the image become more pronounced.
Moving in any of the triangles above the input boxes will change the values in the boxes. You
can observe how the values in the boxes are affected by moving the triangles, or you can enter
values into the boxes directly. In both cases, the histogram will change accordingly.
4
The
Histogram bar
distribution of shades changes as you move any of the triangles.
5
Output edit
boxes show the 0-to-255 pixel range to where the Input levels are mapped. For
example, if you modified input values to 30 and 255 and then change output values to 0 to
250, the input values of 30 to 255 will be "stretched" to fit the output range of 0 to 250. This
means you have a total of 250 shades (250-0=250).
Unless you have very specific effects in mind, users are advised to leave this feature alone, so
everything is always mapped to 255 shades (255-0). You can experiment with this feature to
see what it does, however, and how it interacts with the input levels.
6
The
Original / Enhanced
image was modified; or enhanced, after the image had been modified (with shadows and
highlights or any other tool).
7
The
Channel
button lets you control the Shadow and Highlight settings for a particular color
channel (red, green or blue) or for the Master channel (red, green, and blue simultaneously).
8
Input / Count / Percent
appear only when the cursor is inside the histogram or if a triangle is being moved.
• Input value indicates the color value of the data displayed in the histogram.
• Count value indicates the number of pixels at the Input value. If Input value is 2 and Count
value is 1300, then there are 1300 pixels in the image at the input value of 2.
• Percent value is the percentage of all pixels in the image where color value is less than or
equal to the input value. If Percent is 15% and Input value is 2, it means that 15% of all
pixels in the image have a value of 2 or less.
show how pixels are distributed over the 0-to-255 pixel scale.
shows the distribution of shades from dark to light (left to right). The
box lets you choose which histogram to see: the original, before the
figures provide information about the histogram. The figures will
Reference
59
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