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Re: [OM] Does the 50mm f1.8 open to f2? the 50mm f1.2 open to f1.4?

Subject: Re: [OM] Does the 50mm f1.8 open to f2? the 50mm f1.2 open to f1.4?
From: "John A. Lind" <jlind@xxxxxxxxxxx>
Date: Tue, 03 Jul 2001 12:40:56 +0000
Yes, if you set it between the detents. The last detent is f/1.8 and f/2 has none. BTW, f/1.8 is 1/3rd stop faster than f/2 making a detent for it not all that necessary. Same applies to the faster f/1.2 lens, except f/1.2 is a half stop faster than f/1.4 and you can approximate it if you wish by setting the ring about halfway between the last detent (f/2) and wide open.

I have used half-stop settings in the past on the Zuiko's; it's not a big deal to me that there's no detents for half-stops or third-stops between the full stops.

-- John

At 13:55 7/3/01, Parzival wrote:
The standard series of lens apertures are geometric series with a
square root o 2 (1.4142...) ratio, ie. 1, 1.4, 2, 2.8, 4, ...

The 50mm f1.8 lens has an aperture click stop at f2.8, then a white mark
and a click stop, then the figure 1.8. Does the lens open to f1.8, or f2.0
at the last click stop? If it opens to 1.8, is it possible to set the lens to f2.0?

Of course, truth in advertising would suggest it opens to 1.8.
Trying it out using my OM4T meter, the shutter speed doubles
shifting from f2.8 to the max aperture. If that is f1.8, the meter
should go from 1/250 to 1/600. 1/(250 times (2.8/1.8) squared), i.e
(1/250 times 2.4) or 1/600. But perhaps I can't read the difference
between 1/500 and 1/600 on the OM4T LED.

Anyways the real reason I am splitting this particular hair is
to find out the relative values of the f1.2, and the f1.4 lenses
compared to the f1.8. I don't have an f1.2 I'm just going
by the pictures of the lens. The f1.2 lens has no f1.4  aperture
ring indication, so  presumably if truth in advertising prevails,
the f1.2 lens set at f2.0 opens to the last aperture click stop position
at f1.2, and f1.4, a full stop down, is not readily available.
(Can this be true?)


I think I want an f1.2 but my Jiminy Cricket is chirping "is the $400
or so that this lens is going for now worth the 2 stops?"
(Or is it really 1.5 stops? - hence my question.)  Yes, I know
Skip Williams' data says the average price is $260, but dealers
and recent auctions are asking for and getting more. And
I haven't yet got to the dumpster diving stage of Zuikoholism,
like those of you putting together those $1100 kits with those
really cheap 90mm f2.0s. ;-)

- Parzival


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