My Leitz Super-Angulon f/3.5 21mm in M-mount wasn't cheap, but has only four blades. Those four blades do have to stop down to a very small opening at f/22. In comparison, the many blades of old large format lenses had an opening of several mm at their minimum aperture. These were easier to make and less delicate than that tiny Leitz iris.
Originally Posted by mopar_guy