Logic would suggest that using a wider-than-necessary hood would only result in
possible flare from light outside the FOV cone hitting the front objective.
In the cases you describe, I wouldn't worry. It's not going to vignette,
you're just not the proper, narrow-er hood for the 35 or 50's. Personally, I'd
use the 40/85/100 rubber hood on a 50mm lens, as it is very forgiving re:
dents. And that hood is easy to find.
A potential overlooked issue is that some hoods are designed with a specific
angle of view + front objective set-back (from the hood mounting point) to
maximize the hood's functionality. But I don't think any of the OM lenses or
hoods are built with such deep-set objectives where that would cause a problem.
Some musing on the OM hoods:
The hood for the 28-48/4 seems particularly wide, but you have to remember that
it spans a significant focal length and it also rides on the outer 55mm filter
ring.
The aformentioned rubber 40/84/100 hood seems counterintuitive that it should
work on these three lenses; with their widely differing focal lengths. But you
have to remember that the 40mm lens had a front objective element that is VERY
close to the filter ring, so the incoming FOV light cone diverges very quickly
away from the lens. The same hood on the 100/28 sits much further away from
the objective.
The 90/2, 135/4.5 hood is another compromize example, fitting both lenses and
probably optimized for neither.
And don't forget the 21/3.5, 35/2.8-Shift hood. It's very wide, accomodating
the 21mm FOV of the 35-shift lens. If you used a 35 hood on the 35-Shift, you
could be OK; as long as you didn't shift the lens.
As an aside, I have several wide angle lenses (i.e., 35/2.8 CZ Biogon Pre-War)
whose add-on hood is very small and seems too small to help. But when you
couple it with the extremely deep-set front objective, it works.
Geez. I didn't know I was so long-winded on hoods. Maybe it's time to go home?
Skip
Original Message:
-----------------
From: Bill Stanke bstanke@xxxxxxxxxxxx
Date: Thu, 31 May 2001 13:01:29 -0700
To: olympus@xxxxxxxxxxxxxxx
Subject: [OM] Lens Hood question
Hi Zuiks:
What happens if you use the wrong shade on a lens - vignetting?
Specifically, if I use the hood for a 28 mm /F2.8, 28 mm /F3.5
(#108-221) on a 35 mm /F2.8 or 50 mm /F1.8. I notice that the 35 mm
and 50 mm have a different part number (108-230), but is there a
function difference?
Thanks!
Bill Stanke
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