In a message dated 2000-03-18 2:37:32 AM Eastern Standard Time,
jlind@xxxxxxxxxxx writes:
<< At 03:29 3/17/00 , Alex wrote:
>the Germans seem to really be into. Some cases in point are the highly
>regarded 50F1.4 lens has only 6 diaphragm blades to everyone else's 8,
there
Hmmmm, my Contax 50/1.5 has eleven blades. But it's a Carl Zeiss Sonnar
for the original Zeiss Ikon RF. Anyway, having examined the lens and its
blade operation throughout its range, I came to the conclusion it's not as
much how many blades there are, but the shape of the aperture opening as
the lens stops down. It has exceptional bokeh except about a one-stop
range right in the middle of its aperture range. Obviously it's easier to
maintain a more circular aperture with more blades, but even with eight on
the 50mm Zuiko's I have images that show the effect of their straight edges
when stopped down. Even then it's not the only thing that affects lens
bokeh. There are other effects such as coma, and even with flat sides
creating a hexagon or octagon some lenses seem to have good bokeh in spite
of it.
-- John
>>
I agree John, that blade count is only one of a number of things that go into
consideration. But a high blade count at least suggest the designers gave
some attention to bokeh. Contax does not list diaphram count as a spec
anywhere on their web site! I'm also surprised that Mamiya could come out
with the 7 rangefinder and only "5" diaphragm blades in this day and age!
Alex
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