Hello Dean,
Thank you for your information and reminding me of the effects of diffraction.
However, the degree to which this may be a problem possibly depends on
the design of individual lenses. I don't know.
According to Gary Reese's tests at
http://members.aol.com/olympusom/lenstests/default.htm
the Zuiko 100/2 should be sharp (A-) at f/22.
Perhaps I might try a set of tests - now that I have my own film scanner (HP
Photosmart) I can bypass the lottery of lab scanning as well as their costs.
The yellow flag iris is over for this year however ;-(
A nice big flower with lots of interesting detail and colour, if the light is
carefully controlled.
What I wanted to highlight however, was that the combination of long lens
(versus short lens), no aperture pre-fire, and a slow shutter speed, even for a
lens renowned for being sharp, could have an observable downside. I think
that if I were to try this again with the OM1 I would firmly fasten a very
heavy
weight to the camera to absorb the vibrations through the inertia of the weight.
The Panagor doesn't go smaller than f/16, and f/22 is the smallest aperture
for the Z 100/2. Maybe I should have used the same aperture for both.
I wanted to capture the greatest depth of field for this flower which, as those
who have seen it will appreciate, has considerable diameter, and was
interested to compare what these two lenses could offer. I did not expect
significantly different resolution at the zone of sharpest focus.
Of course, what I could have done is what a professional photographer friend
of mine says, as he pokes fun of my purchasing ever "more bits of bottle", as
he puts it. This is to use a medium format camera - his choice would be
Hasselblad - fit a standard lens, stand back a bit, and shoot. From the ample
negative I could crop and enlarge, have all the flower in focus from front to
back, and heaps of definition. Take your pick. I don't have a 'blad.
Brian
Date sent: Sat, 15 Jan 2005 21:46:58 -0800
From: "Dean C. Hansen" <hanse112@xxxxxxxxxx>
Send reply to: Dean C Hansen <hanse112@xxxxxxxxxx>
To: bj@xxxxxxxxxxxxxxx
Subject: Re: resolution of images
> Hi Brian,
> I read your post on the recent OM post and have an observation to
> share: did you shoot the Pangor at f16 and the OM at f22? It's not
> completely clear to me from your post if this is the case. If so,
> however, I'd suggest that you've run into diffraction degrading your
> image. I don't shoot my 38/2.8 OM macro lens at anything smaller than
> f11. I've compared shots at f8, f11, f16, and f22 of the same subject,
> and the degradation in resolution when going from f11 to f16 is
> noticable. Ditto for the 20/2 OM macro lens--at full extension on the
> bellows, one gets degradation at anything smaller than f2.8! "Always
> stop down for maximum depth of field" is an oft-repeated dogma that
> simply is very misleading. OK, maybe DOF increases, but if the overall
> resolution decreases, because of increased diffraction, what's to be
> gained? Try the Pangor and OM at f8, f11, f16, and f22 on that iris
> (our native ones are blue, not yellow, here in Minnesota) and compare
> image resolution at the various f-stops. My thought is that you'll see
> degradation at those small aperatures, and that the degradation is due
> to the laws of physics rather than lens quality.
> Best wishes,
> Dean
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