Improving image quality on IMX477

[caphector]

I set up indi-allsky to run a camera I set up for a few different reasons, including using it as a weather cam, plane-spotting, and astronomical observations. As part of this I'd like to get naturalistic images during the day, but even after tweaking settings I'm still getting color casts and I wanted to see if I was missing a better way to improve color fidelity.

I have an IMX477 camera; I currently have it configured in DNG mode with AWB enabled and R/G/B 3.22/1.0/1.5 and Bayer set manually at BGGR (FWIW, changing from Auto Detect to BGGR improved visual quality enough that I started tweaking the balance factors). This is an example of what I see from indi-allsky on the left and from raspistill on the right:

These were taken at about the same time. Whenever I look at the levels in the indi-allsky image they're oddly peaky as well:

[aaronwmorris]

Does your camera have the IR/cut filter?

[aaronwmorris]

The exposure banding ("stepping" might be a better word) as you called it is pretty normal for the morning and evening when there are drastic changes in lighting. It will crop up as the sun or moon moves across the view, because they skew the ADU values.

Exposure flapping is a different phenomenon. When the exposure algorithm needs to calculate a new exposure, sometimes it will get stuck between two exposures trying to find a stable value and "flap" back and forth which results in a strobe effect. This usually only happens during the day, at extremely low exposure values.

[caphector]

Is there anything I can do to pull more detail out of bright areas? I've noticed that in bright area detail gets bloomed out and I wonder if more detail can be recovered.

I've been slowly lowering my gain, but since the camera is shooting DNG would it be possible to use a image direct off the sensor to test different image settings? While I don't mind the current process it would be nice to compare settings changes against the same image rather than checking after the fact.

[aaronwmorris]

Testing settings with a RAW file is one of the things I would like to add soon.

There is probably not much that can be done with bright areas. When you have things like clouds pass by and their brightness is too high, they just end up being overexposed. If you increase/decrease the exposure, the clouds will be normalized and the rest of the image will be too dark.

You can try the stretching option, but I doubt it will do anything to fix areas being too bright. CLAHE contrast enhance might help a little, but that can have some weird side effects.

You have some pretty gnarly lights that are shining on the dome that is killing your contrast.

[caphector]

Yeah; I need to get the camera on the side of the roof away from the streetlights, but that requires getting power up there as well. I'll put that on the To Do list. I'd hoped that painting the edges of the dome black to cut down on glare would help, but no dice.

[caphector]

Got it moved to the dark side of the roof. Helpfully, the moon was nearly full when I moved it but I'm looking forward to seeing star trails getting generated again once it wanes a bit.

I'll need to start poking the gain settings again; would be nice to have the sky center closer to black to pull the corners brightness down further.

[caphector]

Thanks for the explanation and for confirming that the behavior is normal; the visual look of the exposure change in the timelapse in particular made me wonder if it was flapping.