Chuck Norcutt wrote:
> Thanks for the correction. I had thought the prevalence of 35mm as the
> common wide angle years ago was that it was the minimum focal length
> non-retrofocus design.
>
I think it was a hangover from rangefinders, where 35mm was a standard
focal length and the lenses didn't have to be retrofocus. Remember when
a "full" WA to tele kit was 35, 50, 135mm?
If you look at the cross sections, you can see how all the 50mm lenses
are variations on the D-G symmetrical design, with the 50/3.5 needing
one less element for the smaller aperture, the 50/1.2 & 1.4 adding one
for the extra speed and the 50/2 macro adding three. Notice how all of
them have a lozenge/almond shaped open space right in the middle. The
40/2 is clearly of the same sort, while the 35s are clearly not, with a
cemented triplet element in the center.
If you look at the cross section of the E-P1. you will see that there is
so little distance from front flange to shutter unit that the 17/2.8,
assuming it is a D-G, non-retrofocus design, probably almost touches the
shutter. <http://www.olympus-global.com/en/news/2009a/nr090616ep1e.cfm>
Moose
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