7.10 Auto Exposure; Auto_Exposure: 804H - Point Grey Flea3 FL3-U3 Technical Reference Manual

Point Grey Flea3 USB 3.0 Technical Reference
//Ensure auto-adjust mode is off.
prop.autoManualMode = false;
//Ensure the property is set up to use absolute value control.
prop.absControl = true;
//Set the absolute value of shutter to 20 ms.
prop.absValue = 20;
//Set the property.
error = cam.SetProperty( &prop );

7.10 Auto Exposure

Auto exposure allows the camera to automatically control shutter and/or gain in order to achieve a specific average
image intensity.
Auto Exposure allows the user to control the camera system's automatic exposure algorithm. It has three useful
states:
State
Off
ON
Manual Exposure Control
ON
Auto Exposure Control
Auto Exposure can only control the exposure when Shutter and/or Gain are set to automatic. If only one of the
settings is in "auto" mode then the auto exposure controller attempts to control the image intensity using just that one
setting. If both of these settings are in "auto" mode the auto exposure controller uses a shutter-before-gain heuristic
to try and maximize the signal-to-noise ratio by favoring a longer shutter time over a larger gain value.
In absolute mode, an exposure value (EV) of 0 indicates the average intensity of the image is 18% of 1023 (18% gray).
The auto exposure algorithm is only applied to the active region of interest, and not the entire array of active pixels.
Auto Exposure ROI —Allows the user to specify a region of interest within the full image to be used for both auto
exposure and white balance. The ROI position and size are relative to the transmitted image. If the request ROI is of
zero width or height, the entire image is used.
7.10.1

AUTO_EXPOSURE: 804h

Formulas for converting the fixed point (relative) values to floating point (absolute) values are not
provided. Users wishing to work with real-world values should refer to Absolute Value CSRs
148).
Revised 9/27/2012
Copyright ©2011-2012 Point Grey Research Inc.
Control of the exposure is achieved via setting both shutter and gain. This mode is achieved by
setting Auto Exposure to Off, or by setting Shutter and Gain to Manual.
The camera automatically modifies Shutter and Gain to try to match the average image intensity
to the Auto Exposure value. This mode is achieved by setting Auto Exposure to Manual and
either/both of Shutter and Gain to Automatic.
The camera automatically modifies the value in order to produce an image that is visually
pleasing. This mode is achieved by setting the all three of Auto Exposure, Shutter, and Gain to
Automatic. In this mode, the value reflects the average image intensity.
7 Imaging Parameters and Control
Description
(page
114