I'm recording images with a Raspberry Pi 4, a Raspberry Pi HQ camera and the v4l2-ctl calls. A while ago I was using picamera for Python and it was no problem setting a fixed exposure, resulting in the same brightness under the same recording conditions, as can be seen in this time series of images:
I then had to switch to v4l2 and I am using these settings:
v4l2-ctl -c auto_exposure=1 # Manual exposure
v4l2-ctl -c iso_sensitivity_auto=0 # Manual ISO
v4l2-ctl -c iso_sensitivity=1 # low sensitivity
v4l2-ctl -c exposure_time_absolute=4000
v4l2-ctl --set-fmt-video=width=4056,height=3040,pixelformat=3
v4l2-ctl --stream-mmap=3 --stream-count=1 --stream-to=...
However, even though exposure and ISO should be fixed, the brightness of recorded images varies dramatically:
Can I address this somehow?