User Manual - twentynine
5.2.3
Automatic Exposure and Gain Control
Cameras are often used in different environments and applications with changing conditions, such as
scene illumination which may vary and change constantly. At certain aperture size, exposure time and gain
values, the image captured by the camera can be underexposed (too dark) or overexposed (too bright), thus
losing image details. As described in previous chapters the image brightness can be adjusted by changing
exposure time and gain values. The SMARTEK Vision twentynine camera series provides on-camera
automatic control of exposure time and gain, thus automatically adjusting the values within defined limits,
until the specified target image brightness is reached.
The operation of the automatic exposure and automatic gain algorithms can be controlled via the properties
ExposureAuto
, adjusting the exposure, and
GainAuto
, adjusting the gain of the camera. Both have three
operation modes, listed in Table 23.
Value
Description
Off
Automatic mode is disabled; exposure and gain can be set manually via the
ExposureTime
and
Gain
properties
Once
Automatic Exposure/Gain is done once until the target gray value is reached,
the operation mode is then set to
Off
Continuous
Automatic Exposure/Gain algorithm is running continuously
Table 23: ExposureAuto and GainAuto operation modes
In case when both
ExposureAuto
and
GainAuto
are set to
Continuous
mode, the automatic control
algorithm always tries to achieve the smallest gain value to keep the noise level as low as possible.
Parameters that control
Automatic Exposure
and
Automatic Gain
features are listed in the following table:
Parameter
Type
Description
TargetGrayValue
Integer
The average image brightness that should be reached
ExposureTimeAbsLowerLimit
Float
The minimum exposure time (in
µ
s) that is allowed to be
set by the
Automatic Exposure
algorithm
ExposureTimeAbsUpperLimit
Float
The maximum exposure time (in
µ
s) that is allowed to be
set by the
Automatic Exposure
algorithm
GainAbsLowerLimit
Float
The minimum gain value (in dB) that is allowed to be set
by the
Automatic Gain
algorithm
GainAbsUpperLimit
Float
The maximum gain value (in dB) that is allowed to be set
by the
Automatic Gain
algorithm
Table 24: Automatic functions parameters
For cameras that do not support on-camera automatic exposure and automatic gain control, the automatic
adjustment of the camera’s exposure time and gain within user application can be realized by using the
ImageProcAPI provided by the CameraSuite SDK. For detailed description of the automatic exposure and
gain features in the SDK please refer to chapter
8.2.3 - Auto Exposure and Auto Gain
.
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SMARTEK Vision | User Manual - twentynine | Doc. v1.0.2
