Pentax Optio P80 Operating Manual page 29

When the image is too dark, the part to the left is cut off (dark portions)
and when the image is too bright, the part to the right is cut off (bright
portions).
Understanding Contrast
The graph peaks gradually for images in which contrast is balanced. The
graph peaks on both sides but sinks in the middle for images with a large
difference in contrast and low amounts of mid-level brightness.
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