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[OM] computing lens hood dimensions

Subject: [OM] computing lens hood dimensions
From: William Sommerwerck <williams@xxxxxxxxxx>
Date: Fri, 02 Oct 1998 06:47:06 -0700
"I don't think that a simple formula would suffice for deciding which
hood will suit which lens; the distance back of the front glass (I don't
know whether to call it lens, group or element) or the "glass relief"
(?) will be as important as the angle of acceptance of the lens as a
whole. I got caught out when I used a 28/2.8 hood on my 28/2 - there was
no darkening of the corners, it was masked off! It was a pity because it
was a lovely old church in Italy."


You've got the right idea. The lens hood dimensions are determined not
just by the angle of view of the lens, but also by where the hood sits
with respect to the lens's entrance pupil. The farther the entrance
pupil is from the front of the lens, the more likely a given lens hood
is to vignette. (If this is wrong, would someone please correct me?)

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