The auto-diaphragm must be a big determinant in the number of blades.
My impression is that most manual/preset lenses have alot of blades. My
old preset 105 2.8 has 14 of them, forming a near-perfect circle at all
settings.
The quick-return diaphragm is relatively complicated compared to a
manual one. . . .I think it took Asahi a couple of years to perfect
theirs after they brought out the original Pentax. The first Canonflex
SLR's used a charging pin . . . . when you wound the film you also
pre-tensioned the diaphragm. If more blades equals better optics, then
are most modern lenses a compromise?
Morgan Sparks
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