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[OM] Re: Free OM-to-E-System adapter?!

Subject: [OM] Re: Free OM-to-E-System adapter?!
From: Tim Hughes <timhughes@xxxxxxxx>
Date: Sat, 17 Jan 2004 18:55:02 -0800 (PST)
Winsor wrote:
 >>    I wonder if it is related to the diffusion layer that is frequently used 
 >> to limit moire.
Maybe the diffusion also flattens out the brightness a bit. 
<<
I don't believe it was in relation to the anti-alias filter you mention.
The comment was an aside but my impression was it was related to the geometry 
of the exit aperture
of the faster lens at full aperture interacting with the aperture of the on 
chip lens, causing
light to not focus completely onto sensor. 

Another interesting aspect of on chip lenses is that they need to be angled 
from edge to be fully
effective. Whether this is actually done since this is probably a lot trickier 
to manufacture, is
another question. Also this may mean this is a compromise for long FL lenses 
versus short.

>> 
I also wonder whether the exposure circuitry takes the fast lens fall 
off into account. Is it an even fall off or does it also get worse 
toward the edge?
<<
If the exposure sensors are seperate (off sub mirror for slr etc) then probably 
not, unless sensor
lens speed is factored in under software.

>
>  The CMOS Foveon sensor should theoretically be much better in regards 
> to using non-digital lenses as the wells  are much shallower and the 
> sensor area is at least 3 times larger per pixel, dramatically reducing the 
> bottom of the well 
> effects.

>>I have wondered about part of that. While the top sensor may be very 
shallow and unlike a well, wouldn't the bottom one be in a well? 
<<
My reading of the pattent some time ago, is they are pretty shallow as you 
might expect, based on
these are wavelength related absorbtion effects. You can check the drawings on 
the USPT office
website. (you need to download a special TIFF viewer) In any case the area is 
much larger and
diameter of the well ~three times larger, which would mean the well would need 
to be three times
deeper to be approx as bad as normal sensor.

Interesting that Foveon has not made claims about working better with 
"non-digital" lenses.

Regards,
Tim Hughes


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