OV9281 minimum exposure in manual much higher than in auto

  1. Where did you get the camera module(s)?
    3rd party online retailer.

  2. Model number of the product(s)?
    OV9281 (B0332)

  3. What hardware/platform were you working on?
    Linux, Windows

  4. Instructions you have followed. (link/manual/etc.)
    Adjust the minimum exposure time - Arducam Wiki

  5. Problems you were having?
    I’d like to take tune the camera to work under a bright light in fixed conditions, but when the camera is in manual exposure mode, the lowest exposure setting is still much higher than what the camera can reach in auto mode. As a result, I can’t get a good image in manual mode.

Images below were taken in identical conditions, both under a bright light.

Left: auto (auto_exposure=3 in v4l2)
Right: manual (auto_exposure=1 and exposure_time_absolute=1 in v4l2)

On Windows the numbers are different, but the results are the same.
Correction: Results on Windows are considerably better, but still not as good as auto exposure.

  1. The dmesg log from your hardware?
    Hardware seems irrelevant, tried different machines, and different OSes.

  2. Troubleshooting attempts you’ve made?
    Checked every capture format and frame rate. Tried using the camera with OpenCV, in VLC, and in AMCap. All have the same problem.

  3. What help do you need?
    Is there any way to adjust the manual exposure to the level it can reach in auto, below what v4l2 reports as the minimum value?