RE: [Leica] R8/R9 Digital Back announced

["Austin Franklin" <darkroom@ix.netcom.com>]

Hi Aaron,

>  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.

You are correct.

  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.

Not quite.  It's the wide angle lenses that are the problem, and they, even
for SLRs, still have vignetting problems with full frame sensors.  Why most
digital SLRs don't show this problem is the sensor is in fact half the size
of 35mm film...and therefore doesn't use the light outside that region.

> 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.

That is correct.  Think Fresnel ;-)

Austin

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