It is probably a dust bunny, with a bit of luck it will move on its own accord. To be honest i would set the rear cameras to colour only anyway because it seems to perform much better, all the hype about the monochrome sensor adding detail etc. is marketing guff in my opinion, i would much rather have had another colour sensor at a different focal length.
I wouldn't even use it with the colour sensor, it is a badly conceived idea that works badly in practice. I have lots of photos with what is best described as a shadow and it is when a moving subject is seen differently by 2 sensors trying to work as one.
@ Gary and MrBelter,
I'm curious, can you attach a cropped sample or a link to a picture with the issues you got, please?
(Posts with links may take a while before they appear in the forum).
What appear to be smudge could be light reflecting in the lenses, maybe? Strange things can happen in low light when the algorithms work overtime.
Only the colour sensor has OIS, which may cause alignment issues, but HDR can also explain shadow effects on moving objects?
I still haven't figured out how to determine if and when both camera sensors on Nokia 8 are actually used, but HDR in auto mode does not always produce the kind of picture I want.
I believe it's HDR ghosts in your sample, not a twin camera issue.
The various modes is in the original .jpg file EXIF properties Camera > Software - which is overwritten when the picture is edited.
I suggest try toggle off HDR instead and see how it goes?
There's some impressive processing going on, also when HDR kick in, but small moving objects on a dark background is a challenge.
Only 1 of 30 samples in full auto mode or with HDR forced on had a tiny HDR ghost during my testing. It could be much worse:
I have been unable to post a image when on the site on my Nokia 8. I will post one from my home PC later. It does seem to of got better and less noticeable lately although I only briefly check. Decided to use on the single colour camera now which is fine.