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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