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Re: [OM] one good thing...

Subject: Re: [OM] one good thing...
From: Tom@xxxxxxxxxxxxx
Date: Mon, 28 Jan 2002 13:22:54 -0500
On Monday, January 28, 2002 at 10:09, William Sommerwerck 
<olympus@xxxxxxxxxxxxxxx>
wrote re "[OM] one good thing..." saying:
...
> A word about lens compatibility. The cells in a CCD sensor sit slightly
> below the conductive paths that surround them. This means that, the
> more-acute the angle of light striking the sensor, the greater the shadowing
> effect of the paths, further exaggerating the normal edge falloff that
> occurs with wide-angle lenses.
> 
> Olympus claims their new lens design gets around this problem by moving the
> exit node farther from the film plane, thus making the angle of attack less
> acute. This doesn't sound right -- the angle at which the light rays strike
> the film is, by simple geometry, unavoidably linked to the lens's angle of
> view. How can you make the angle less-acute without simultaneously reducing
> the angle of coverage?
> 
> So I did some research. In every reference I checked, a lens's focal length
> is _defined_ as the distance from the exit node to the film plane. In other
> words, you can't change the position of the node without simultaneously
> changing the lens's focal length. QED -- Olympus's claim is not kosher.

 But what about telephoto and wide angle lenses that alter where the light 
is coming from? Is the exit node of the 8mm 8mm from the film plane?

tOM
------------------------ http://groups.yahoo.com/group/ottawa-photo-clubs
tOM A. Trottier,        ICQ:57647974    http://abacurial.com
        758 Albert St, Ottawa ON Canada K1R 7V8 
        +1 613 860-6633 fax:231-6115 N45.412 W75.714
"The moment one gives close attention to anything, 
even a blade of grass, it becomes a mysterious, 
awesome, indescribably magnificent world in itself -- 
Henry Miller, 1891-1980


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