Archived posting to the Leica Users Group, 2008/08/28
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]George has noted a relevant point though, being the need for more angling by
the peripheral micro lenses to help offset the smaller lens/sensor distance.
There is a processing component to this too, but that requires the camera to
identify the lens in use for best effect.
On the IR absorption filter (.5mm thick) Leica has consciously gone for that
compromise and with less camera firmware processing, in an attempt to retain
as much detail resolution as possible. It proved to be imperfect, as has
been very well publicised. In colour, it affects more than the obvious
synthetic fabric reproduction, there is skin tone pollution too. Plus affect
on the WB in general. Wides are more affected, BW is a different issue, as
is shooting jpg instead of Raw. Part of the reason for this compromise was
to keep compatibility with almost all M lenses made prior to the 6 bit
encoding (there being no electrical communication as you know). It also
meant less diffraction and flare (from internal reflections) potential
issues (all meaning degradation of resolution and contrast)
In practice, superb Leica glass, 6 bit coding, the external UV/IR filters
and the current firmware really make it all a non-issue. Truly the quality
is stunning.
Cheers
Geoff
http://www.pbase.com/hoppyman/e
http://gallery.leica-users.org/v/gh/
-----Original Message-----
Subject: RE: [Leica] Getting close to Photokina... I want tostart anew
rumor....
I don't think that is the correct issue, George.....
The micro lens filter may be needed to correct oblique light rays to get a
better overall flat gain in the sensor stages... but that has nothing to do
with the IR filter ( which may be simply a coating on the microlens filter-
plate).
It is the lack of IR filter that causes Purple - Black Polyester
shirts........ and, to the best of my knowledge, Leica M8 is the singular
( non-P+S) camera to lack this filter The coating, if that is what it is,
is too thin to effect any optical characteristics other than frequency
response........ ( a few microns thick..... ).
.
Frank Filippone
red735i@earthlink.net
the dmr has an IR filter on the sensor
the slr retrofocus wide angles achieve angles closer to 90?
unlike film - sensors prefer light beams coming as close to 90? as
possible.
the issue for the M digital was and is
true wide angle lens designs casting their focused image rays at
severe angles to the sensor.
this required a filter with special offset microlenses on top of the
sensor to reduce vignetting
the questions remain:
how many "filters" do we lay on top of the sensor?
what effect do the filers have on image quality (including the all
important fine micro detail)?
what compromises in image quality do we make?
Fond regards,
George
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