Re: [Leica] R8/R9 Digital Back announced

[Jerry Lehrer <jerryleh@pacbell.net>]

Henning

I am impressed.  The new lenses all must have that "ray-straightener"
built in.

Jerry

Henning Wulff wrote:

> At 11:29 AM -0400 6/27/03, Aaron Sandler wrote:
> >At 10:12 PM 6/26/2003, : "Jim McIntyre" <mcintyre@ca.inter.net> wrote:
> >>If the M camera can mount an M lense, and focus on the film plane, then it
> >>seems logical that that same film plane can be a digital sensor. Am I in
> >>deep space on this?
> >
> >From what I've read, current digital sensors require the light rays
> >to hit them from an "angle of incidence" that is nearly
> >perpendicular to the sensor.  Film, on the other hand, can accept
> >light hitting it at quite an oblique angle.  Wide angle rangefinder
> >lenses, being close to the film plane, send much of the (outer
> >portion of the) image to the film/sensor from an oblique angle.
> >Therefore they work for film, but not with current digital sensors.
> >SLR wide angle lenses (which are of retrofocal design, meaning they
> >have elements designed to bend the light rays back into being mostly
> >parallel with each other in order that the rays of interest still
> >all hit the film after travelling the additional distance to
> >accommodate the mirror) send all of their image to the film/sensor
> >at a pretty-close-to perpendicular angle of incidence.  Therefore
> >they work for film and current digital sensors.  Anyway, that's my
> >understanding.
> >
> >For this reason it seems folks are pretty down on the possibilities
> >of using M lenses with digital capture, at least without some kludgy
> >retrofocus add-on that would degrade image quality, make the system
> >much larger, and generally mess up most of the advantages of M
> >lenses.  Recent messages haven't actually used the word
> >"impossible," but that's the feeling that seems to be conveyed.
> >
> >However, it seems to me that the inability of current sensors to
> >capture oblique light doesn't mean future sensors won't be able to.
> >Plenty of "impossible" things have been accomplished.  Ok, so it
> >might be another decade until the right sensor is made...but I, for
> >one, can wait.  I just hope someone bothers to do it.
>
> That pretty much covers it; although, once again, it's all in the archives :-).
>
> M wide and even the 50 lenses have very oblique rays in the corners,
> so even digital sensors that are half frame can't handle the light
> that comes from these lenses.
>
> One of the problems that has been noted with 'film' lenses on the
> Canon 1Ds is that colour fringing has shown up in the corners with
> much greater apparent severity than on film, purportedly bolstering
> the argument that the 1Ds needs 'higher quality' glass than film
> cameras. This is due to three reasons as far as I can tell; one, the
> oblique ray issue, and: two, the fact that the light rays get
> 'digitized', so that even minor fringing can cause adjacent pixels
> (or Bayer cells) to register vastly different colours and: three,
> that the sensors in most digital cameras, but particularly full fram
> sensors, need little 'lenses' to be able to handle any oblique rays
> whatsoever. These cause some further chromatic problems at light
> strikes them obliquely. Analogue (film) sensors provide a smooth
> transition and doesn't show the fringing that all lenses produce as
> easily.
>
> Have a look at a schematic lens design for the new Olympus 4/3 camera:
>
> http://www.steves-digicams.com/2003_reviews/e1_pg2.html
>
> about 2/3 of the way down the page. See the light rays at the rear of
> the lens. That is what Olympus considers ideal. M lenses are about as
> far from that as anything made. The designs that allow outstanding
> lenses such as the 21/2.8 ASPH kills those same lenses for present
> digital image sensors.
>
> --
>     *            Henning J. Wulff
>    /|\      Wulff Photography & Design
>   /###\   mailto:henningw@archiphoto.com
>   |[ ]|     http://www.archiphoto.com
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