At 11:11 PM +0000 6/25/03, olympus-digest wrote:
>Date: Wed, 25 Jun 2003 13:25:57 -0700
>From: "Jeff Keller" <jrk_om@xxxxxxxxxxx>
>Subject: Telecentric requires larger lens backside? Re: [OM] Some info on the
>new E-1
>
>Having thought about this for awhile I still don't get it...
>
>Doesn't a retrofocus design and the goal of what Olympus wanted to
>achieve imply that the light striking the CCD is closer to perpendicular
>and therefore the light as it leaves the lens will be closer to the
>axis ---> smaller diameter lens mount?
Only if very slow lenses are OK. With large apertures like f/1.4 the
converging cone of light is a bit fat. That, combined with the required
distance from the back of the lens to the CCD surface, forces the back lens
element to be larger than the CCD.
>Looking at this from another viewpoint doesn't a RF 35mm such as Lei*a
>have smaller lenses with smaller diameter than typical for retrofocus
>SLR designs?
This is because not having a mirror in the way, they can get closer to the
film, and also because it doesn't much matter if the light from the lens hits
the film at an angle.
Joe Gwinn
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