was confused about why my dark frames had a large structure, as if a light leak were present. On the camera there was an RF 70–200 f/2.8. After doing some googling, I found out that Canon itself installs infrared lights inside the lenses. With the 200–500 this is not a problem, but with the 70–200 it completely ruins the darks. Dark frames taken with an H-alpha clip in filter are also clean.
I don’t know whether this is a known problem, but I was really quite astonished.
https://kolarivision.com/canon-mirrorless-rf-lens-internal-infrared-led-fact-or-fiction/
by Ri4Fu
1 Comment
When taking dark frames remove the lenses and close the body of the camera.
You need the same settings,exposure time and temperature like on your light frames,no need to have the lenses attached on.