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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