Some lenses contain an IR LED (infra-red) module which can leak IR light affecting long exposures - it's very obvious with modified cameras.
I don't think it's a well-known problem in the astro-community, which is why I'm starting this thread to gather further information and to make the issue more widely known.
It recently came up here in this thread, in which there are numerous examples:
What is going on with my sensor?
KolariVision has also noticed the problem:
Canon RF lens internal IR LED: Fact or Fiction?
So far, we have clear examples from both Nikon and Canon lenses.
If you notice this leak in a long exposure dark frame then one possible way to confirm it is a lens problem is to tape over the electrical contacts before attaching the lens to prevent power reaching the lens. Then re-take the dark and see the the problem goes away. I'm not suggesting this is a sensible solution - it's simply a method of diagnosis. Since the lens cannot be detected by the camera, you may also need to go into the camera's menu to allow it to shoot without lens.
If you have any examples or solutions then please post them here. It will be interesting to find out how widespread this problem is and what, if anything, can be done about it.
Edited by sharkmelley, 04 July 2020 - 03:42 AM.