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Re: [OM] E-P1 - more leaked pictures

Subject: Re: [OM] E-P1 - more leaked pictures
From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
Date: Tue, 16 Jun 2009 08:12:53 -0400
Thanks for the correction.  I had thought the prevalence of 35mm as the 
common wide angle years ago was that it was the minimum focal length 
non-retrofocus design.

Chuck Norcutt

Moose wrote:
> Chuck Norcutt wrote:
>> No, I think it was just the one most easily built... in 35mm format.
>>   
> 
> A little more than that, I think. The way to build a small, light 
> "pancake" lens is to use a symmetrical, double Gauss design. In (D)SLRs, 
> that limits the focal length because of the need to clear the mirror. 
> Typically for FF, that meant a minimum FL of about 40mm, like the 40/2 
> Zuiko. Anything shorter has to be retrofocus and immediately becomes a 
> more complex optical formula and larger lens.
> 
> With no mirror, I suppose m4/3 could theoretically have a D-G formula of 
> shorter focal length, but it would have to actually be sunk far down 
> into the camera body, which raises all sorts of design and control 
> issues. So I would guess that 17mm is the shortest practical 
> non-retrofocus focal length for m4/3.
> 
> m4/3 has a 20mm register distance. If you look at the leaked images, it 
> looks like the front element of the 17mm lens is already deeply recesed, 
> apparently close to the depth of the front of the camera, as is 
> necessary for a non-retrofocus design with a FL sorter than the register 
> distance.
> 
> Moose
>> Ken Norton wrote:
>>   
>>>> What I wonder is why isn't the prime a 10.5mm f/2 which, for m4/3,
>>>> should be much easier to produce than a 21/2 for OM.
>>>>
>>>>       
>>> Because a moderate wideangle (35mm on 35mm format equivalent) is the most
>>> usable lens. If I had only one lens, that is the focal length I'd
>>> choose--not a 21mm equivalent.
>>>
>>> Besides, you gotta have something introduced later to keep the buying going.
>>>
>>> AG
>>>     
> 
-- 
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