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[OM] Re: 35-70 magic shade

Subject: [OM] Re: 35-70 magic shade
From: Jim Brokaw <jbrokaw@xxxxxxxx>
Date: Thu, 08 Apr 2004 22:56:36 -0700
on 4/8/04 4:42 PM, Rob Harrison at robhar@xxxxxx wrote:

> 
> How does the shade for the 35-70/3.6 magically adjust to the focal
> length? Would this shade work in the same way on another 35-70,
> (specifically the 3.5-4.5) or is it tied to the rim of that particular
> lens somehow?
> 
> Thanks!
> 
> Rob Harrison
> Seattle

Rob - The shade by itself doesn't do anything. When paired with the
35-70/3.6 the magic begins. The lens has a rim where the shade clamps on.
The front end of the lens is different from this rim... and when you zoom
from 70 towards 35 the front end of the lens moves out (away from the camera
body, the lens gets longer). This has the effect of moving the front element
of the lens closer to the front of the lens shade, so the wider angle of
view is still shaded just enough by the shade. When you zoom towards 70, the
front element of the lens moves in, toward the camera body... but the front
edge of the shade stays in the same location relative to the camera body.
This had the effect of putting the front lens element 'deeper' in the shade,
since the 70 angle of view is narrower there still is just the right amount
of flare protection.

All zoom lenses should have been designed this way, otherwise their lens
shade is at its best effectiveness only at the widest zoom setting.
-- 

Jim Brokaw
OM-'s of all sorts, and no OM-oney...




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