Sony NEX-EA50 NXCAM, Руководство пользователя

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109%
CCD/CMOS Censor
Saturated Level
Knee point
Knee slope
Input
Output
Without Knee function With Knee function
40 40
What is knee correction?
Cameras are not good at clearly capturing a scene that
contains extremely different luminance levels, such as one
object under bright sunlight and another in the shade. If you
adjust the iris to set the right exposure for the object in the
shade, the object under the sun will be captured too brightly
and appear as a plain white object without texture or gradation.
Knee correction is a function necessary to capture these
images with a wide gap in luminance levels within the standard
range of video signal levels. Just as black gamma influences
contrast in dark image areas, knee correction deals with
contrast in image areas with high luminance levels.
CCD and CMOS sensors can handle an extremely bright input
signal. To output it as a video signal, however, we need to keep the signal within the standard range for video. For this reason,
the signal output level is kept lower than the signal input level
in high-luminance areas that generate input signals beyond
a certain level. In the chart below, the line bends like a knee
at a point in the high-luminance range. This is called the knee
point. And the line extending from the knee point is called the
knee slope. By changing the position of the knee point and the
inclination of the knee slope, contrast in the high-luminance
range can be altered.
The breadth of input signal levels that a system can process is
called the dynamic range. The input signal should stay within
the approximately 109% (white clip point) dynamic range.
PICTURE PROFILE