iXM-GS120 Operation Guide
3. Camera Features
Page 8 of
3.2 Black Reference
3.2.1 Understanding Black Reference
A black reference is the process of reading the sensor output during an exposure without the sensor being exposed to light. This
data is written to the camera and subtracted from regular captures to filter out sensor noise.
Updating the black reference data whenever possible enhances the image quality, particularly when shooting in conditions where
the camera temperature fluctuates. If the exposure time varies considerably, the black calibration reference data should be
updated.
To ensure exposure accuracy, a black reference capture should be made before starting your first flight line, or if exposure settings
or ISO have been changed. This is best done before starting a new flight line, when images are not being captured.
3.2.2 Hardware Activation of Black Reference
If you are building your own hardware control box, you can update the black reference data in the camera. The black reference
control signal should be kept low while an image capture cycle is initiated. The signal must remain low for the full capture cycle.
This makes it possible to create a black reference whenever it is convenient (such as when turning an aircraft around or between
flight lines). When the force black signal is kept high, the camera uses the last updated black reference data.
Black reference timing is shown in the following figure.
in some cases, enabling low power mode (see Section 11.5 Setting When Low Power Mode) can cause slowness in capture rate
when the image capture rate is slower than the low power mode timing. If, for example, the capture rate is scheduled at 15
seconds and the low power mode is set at 10 seconds, each capture will be delayed by up to 350mS. As a result, the capture
rate will be 15.35 S/F instead of 15 S/F in order to allow the camera to exit low power mode. If the capture rate is crucial,
disable low power mode or use hardware wakeup signal.
Note
Black reference is performed automatically with the first shot after switching the camera on.
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