Archived posting to the Leica Users Group, 2004/10/01

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Subject: [Leica] Re: Digital R-Module - hands on
From: frank.dernie at (FRANK DERNIE)
Date: Fri Oct 1 05:16:17 2004

The actual angle of incidence varies for each lens and
is always a cone of rays not a single ray, at wide
apertures and short focal lengths it is a pretty big
cone too. At what pixel density the effect is
negligible I have never seen discussed, it probably
means any low pass filter in front of the sensor can
never be optimised for a wide range of lenses. If the
sensor site wells are not very deep and there is no
filter perhaps it is within acceptable tolerance for
most lenses. Real published data would help quieten
the speculation.
>From a geometrical point of view the idea that all
retrofocus lenses  are OK and that other short focal
length lenses are not seems to be a considerable over
It is certainly the case that any correcting prisms
could only correct for one angle, at all others they
would to an extent be worse - at what point this
becomes negligible needs real data to evaluate.

--- wrote: 
> Frank Dernie wrote:
> > surely there's the rub, if there is a prism there
> suitable for the 15 
> > it will distort the rays from longer lenses, etc..
> > 
> On 30 Sep, 2004, at 20:30, JCB wrote:
> >> Under the glass is a low pass filter and possibly
> a ray bending prism 
> >> glass so that you may use a leica 15mm lens and
> get a reasonable image 
> >> out to the edge.
> Being retrofocus designs the R wide lenses won't
> need any ray-bending
> at the sensor surely?  Isn't that only required for
> the M lenses that
> protrude into the body?
> Simon.
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In reply to: Message from simonogilvie at ( ([Leica] Re: Digital R-Module - hands on)