Erratic Exposure with Canon EOS R5 + Canon RF 15-35mm f/2.8L — Lens Fails to Stop Down
This bug is a disaster when shooting a group of related images, such as an aperture series, focus bracketing, focus stacking, panorama, etc.
Canon EOS R5: Erratic Exposure Due to Failure of Lens to Stop Down
An apertures is shown with perfect matching exposures at f/2.8, f/5.6, f/8, f/11, but an f/4 which is wrong.
I have a tentative diagnosis—it appears that it is a failure of the lens to stop down. What I am as yet unsure of is whether it is lens specific (model, sample), or whether it is a firmware glitch in the Canon EOS R5. But I saw a similar bug back in 2008, so it appears that the bad/buggy code may have carried over into Canon mirrorless.