Get Leica 90mm f/2.2 Thamber-M at B&H Photo.
Twenty aperture blades make for a nearly circular diaphragm. I’ll be shooting the Thambar-M 90mm f/2.2 over the next few weeks. I want to make some unusual images with it as well as see what it can deliver for quality if pressed into service at f/6.3 and f/9.
I rather wish that other vendors would consider this awesome circular aperture, with its 20 blades. Even holding it, one has to look closely to see that it is not quite circular—very impressive.
I’d never use the leather hard case, which also accommodates the center spot filter— a total nuisance in my pack.