Photron FASTCAM Multi, Hardware Manual

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Chapter 4 Functions
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4.9. AUTO EXPOSURE Operation
The system has a function that aut
omatically varies the shutter (the sensor’s exposure time) for
the quantity of light input so that it will achieve the desired image output level.
After the settings are made once, in a situation where settings cannot be changed, this function
displays it
s effect when recording in an environment where the subject’s amount of light changes.
When using this function, the following four items must be set in advance.
"AREA", "TARGET VALUE", "RANGE", "SHUTTER"
Each of these settings is explained below.
AREA
Sets the image area.
The auto exposure function operates so that the average value of the image output level in the area specified
here becomes the desired image output level.
TARGET VALUE
Sets the desired image output level. Set this value as a 10-bit gradation (0 to 1023).
RANGE
Gives the desired image output level a range. Set this value as a 10-bit gradation (0 to 1023).
The auto exposure function operates so that the average value of the image output level in the area specified
here becomes the desired image output level.
SHUTTER
Sets the maximum exposure time. Set in order to prevent subject blur from an exposure time that is too long.

The Auto Exposure function keeps a constant image brightness by varying the shutter speed
(sensor's exposure time).
Therefore, the image may deteriorate as the shutter speed varies from the calibrated setting while
using this function.