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5.5.
Gamma correction
Configure each mode with GAMMA-MODE. There is a
method for setting LUT arbitrarily, and a method for
setting the gamma curve coefficient. There are five
gamma modes from Mode 1 to Mode 5. Apart from
Mode 3, which performs LUT initialization to return the
setting to value at the time of shipment, the modes load
the LUT value saved last time and are capable of
accepting a GAMMA command. After you select a
mode with GAMMA-MODE, input a parameter with a
GAMMA command. You can use the RMEM 2
command to read the LUT setting value. When you set
the mode to Mode 3, the LUT setting is returned to the
value at the time of shipment, but the gamma curve will
be a curve for which an offset of 300 and γ curve of 0.6
has been selected.
Mode
GAMMA-MODE operation
0
OFF (γ=1)
1
Loads last set value
2
Loads last set value
3
Reset to initial value
4
Loads last set value
5
Loads last set value
Note
If the LUT setting is changed in Mode 2 (arbitrary
setting) or Mode 5 (γ coefficient), the LUT setting will
return to its previous configuration after the mode is
switched. If you want to save the setting value, change
the setting in Mode 1 or 4.
However, if you change settings in Mode 1 or 2 after
configuring the γ coefficient, the gamma value and offset
value return to 0. Load setting values as necessary using
the RMEM 2 command.
To return values that you are currently configuring to
their default setting values, use Mode 3 (γ=6, offset 300).
When setting the LUT, configure a 12-bit conversion
value even if you use the camera in 8 bits or 10 bits.
5.5.1.
Arbitrary setting method
The arbitrary setting method is for inputting an LUT
value for an arbitrary value from 0 to 4095. The relation
of level OUT of the output image to level IN of the input
image is expressed by the following equation.
5.5.2.
Coefficient input method
You can use Modes 4 and 5 of GAMMA-MODE to
create your own gamma curve by setting the γ
coefficient and offset value.
Mode settings after SAVE
Saved
Saved
Not saved
Not saved
Saved
Not saved
If the level of the input image is IN (12-bit conversion)
and the coefficient is γ, the level OUT (12-bit
conversion) of the output image is expressed by the
following equation.
The setting range available for the γ coefficient is 0.00 to
1.00.
Setting an offset allows for γ = 1 to be set for the level on
and below the offset, and allows you to prevent white
appearing in black parts.
For example, if you set the offset value to 300, the curve
will be that of γ = 1 for an input image level of 300 and
below, and the curve will be that of the configured γ
value for an input image level over 300. The gamma
curve for all input levels is depicted in the solid line of
the graph, and this curve is used to determine the OUT
level of the output image corresponding to an IN level of
a particular input image.
LUT setting value
GAMMA command
Through (γ=1)
Not possible
Arbitrary setting
Possible
(saved)
Arbitrary setting (not
Possible
saved)
Value at time of
Not possible
shipment (saved)
γ coefficient (saved)
Possible
γ coefficient (not saved)
Possible
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5. DSP Operation
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