I was just looking at a Z mount lens - 24-70mm f2.8 S
The first line of the spec says it is constant f2.8 and has a rounded 9 blade aperture.
If it is a constant f2.8 aperture, why has it got 9 rounded blades ??
This suggests to me that the aperture is adjustable.
If it is adjustable, can someone explain what is meant by constant ?