get_exposure_us() always returns a fixed value

OpenMV Products
1

Hello all,

After the new firmware update, the get_exposure_us() function always seems to be returning 6576 us, even when it clearly increases it to allow for more light. I am using an H7. It used to work perfectly earlier, but not anymore. Any help would be greatly appreciated. :smiley:

2

Which sensor do you have ?

3

OV7725

4

I downgraded to older firmware. Still did not solve the issue. Is there any way to not drop the framerate when the camera view is darker? I don’t mind darker images for my algorithm. But I would need the higher FPS. I went through the sensor control examples, but could not get it to work. Seems like the exposure rate gets fixed according to the initial lighting condition.

For example, I disabled auto whitebalance and auto gain and set
sensor.set_auto_exposure(False, exposure_us =3000)
However, the brightness of the frames varies depending on the initial lighting condition.

5

Yeah, the gain would have locked in on startup. You have to control the gain/white balance too.

6

Thank you for the quick reply :smiley:. I would try it and get back to you.

7

Hey,

I tried controlling the gain, white balance and exposure, But I am still seeing similar results as before, the exposure always depends on the initial lighting condition. Here is the code, am I doing anything wrong here?

sensor.reset() 
sensor.set_pixformat(sensor.GRAYSCALE)   # Set pixel format to GRAYSCALE.
sensor.set_framesize(sensor.QVGA)        # Set frame size to QVGA (320x240).
sensor.set_auto_gain(False, gain_db_ceiling = 5)
sensor.set_auto_whitebal(False, rgb_gain_db = (0.0, 0.0, 0.0))
sensor.set_auto_exposure(False, exposure_us = 3000)
sensor.skip_frames(time = 2000)
8

See this: Method for Full Manual Mode for Sensor OV7725 · Issue #887 · openmv/openmv · GitHub

Another user had the same issue.