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Re: [OM] ( OM ) New zoom lens test uploaded.

Subject: Re: [OM] ( OM ) New zoom lens test uploaded.
From: "John A. Lind" <jlind@xxxxxxxxxxxx>
Date: Sat, 29 Jun 2002 01:11:19 -0500
At 18:27 6/28/02, Jim Brokaw wrote:
Reading further, the review notes that 'half click stops would be nice'.
Having been inside a couple of Zuiko lenses, the aperture clicks are made by
a detent ball riding into slots inside the aperture ring... I suppose you
could add 'half-stops' just by filing additional slots. If done carefully,
they wouldn't show, and if positioned correctly they would probably be close
to really being 1/2 stop spacing. Getting the grooves the right depth and
width might be a little tricky, but I suppose you could make them shallower,
and have them be light stops... maybe I'll sacrifice a 50/1.8 to experiment
with this.
--

Jim Brokaw
OM-1's, -2's, -4's, (no -3's yet) and no OM-oney...

More correct would be 1/3-stop detents, although that's quite a few. Why? The "Speed Value" or SV portion of the Additive Photographic Exposure System (aka EV system) for film speeds is in 1/3-stop increments. "Time Value" or TV is in one-stop increments on nearly all cameras, although some old ones with shutter speeds of 1/25th, 1/50th, 1/100th, 1/200th, 1/1250th etc. are all 1/3-stop from what would be considered standard full-stop increments now. Lens speeds (aperture wide open) at other than full-stop increments are 1/3-stop settings (e.g. f/1.8, f/3.5, f/4.5, f/6.3, etc.). The entire system is geared for 1/3-stop as the smallest increment, including nearly all light meter needle scales and dials (those marked in partial stops).

-- John


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