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[OM] Free OM-to-E-System adapter - Update2

Subject: [OM] Free OM-to-E-System adapter - Update2
From: Jim Terazawa <jimt@xxxxxxxxxxxxxxxx>
Date: Tue, 20 Jan 2004 18:58:52 -0600 (CST)
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Accroding to the table, if I understand the conversion correctly,
the focal lengths and the max aperature will be as follows for
some lenses.
                                                Front element
                                Max f delta     opening diameter
21mm/f2.0 becomes 42mm/f2.8   - One f-stop    : 55mm 
21mm/f3.5 becomes 42mm/f4.0   - Half f-stop ? : 49mm
24mm/f2.0 becomes 48mm/f2.8   - One f-stop    : 55mm
24mm/f2.8 becomes 48mm/f4.0   - One f-stop    : 49mm
50mm/f1.2 becomes 100mm/f4.0  - >3 f-stops    : 49mm
50mm/f1.4 becomes 100mm/f2.8  - Two f-stops   : 49mm
55mm/f1.2 becomes 110mm/f2.8  - >Two f-stops  : 55mm
100mm/f2.0 becomes 200mm/f2.8 - One f-stop    : 55mm
100mm/f2.8 becomes 200mm/f5.6 - Two f-stops   : 49mm
200mm/f4.0 becomes 400mm/f8   - One f-stop    : 55mm
200mm/f5.0 becomes 400mm/f5   - No change     : 49mm

180mm/f2.8 becomes 360mm/f4.0 - One f-stop    : 72mm
180mm/f2.0 becomes 360mm/f2.0 - No change     :100mm
250mm/f2.0 becomes 500mm/f2.8 - No change     :130mm*
350mm/f2.8 becomes 700mm/f2.8 - No change     :130mm*

* estimate since no front filter used.

As stated in the hyperlinked chart notes, the maximum openings are
the recommended f-stops based on calculations done by Olympus
spec.  I assume they are such as considering physical openings
at the front element openings and vignettings, etc.  I think some
max aperatures could be used differently per user..

Jim Terazawa

> Strange indeed, and when you look at the 50f1.2 which becomes a 100f4,
> against the 55f1.2 which becomes a 110f2.8 there are odd things in this
> listing. The 1OOf2 becomes a 200f2.8 for example, so there are nice
> possibilities!
> 
> We'll just have to wait and see for some examples...
> 
> Iwert.
> 
> on 20-01-2004 20:15, Skip Williams at om2@xxxxxxxxxxxxxxxx wrote:
>> 
>> 
>> Most interesting in the hyperlinked chart is the statement that none of the
>> F/2.0 or faster lenses (except the 180/2 & 250/2) allows a maximum aperture 
>> of
>> more than f/2.8.  So you're 50/1.2 becomes a 100/2.8.
>> 
>> So much for using the Zuiko primes as fast telephotos.   And most of the
>> wide-angle lenses lose 1 or 2 stops.  Why?  I guess that by only using the
>> center 1/2 of the light cone, most lenses are hamstrung by not using parallel
>> light rays?
>> 
>> Skip
>> 



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