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

Subject: Re: [OM] E-P1 - more leaked pictures
From: Moose <olymoose@xxxxxxxxx>
Date: Mon, 15 Jun 2009 22:10:14 -0700
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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