EF 300 2.8 IS "1" weirdness
I am using a EOS 6D with EF 300 f/2.8 IS "I".
I put the camera in aperture priority mode and look down the lens barrel, while holding the DOF preview button down and rolling the aperture selector.
The diaphragm looks perfectly healthy, clean, snappy, oil free, as I step through all the aperture settings.
Each change of aperture is a very well defined amount of closure/opening, the progression looks linear and sane. EXCEPT - for f/4.5 to f/5. I swear there is zero change whatsoever between these two aperture settings. EVERY other step is an obvious changes of noticable size. f/4.5 to f/5 - no change.
Can you check your same lens/combo?
Mike in Alaska