On 8/29/2010 4:07 AM, Brian Swale wrote:
>
> I respect Chuck's understanding of statistics and replication, and Wayne's
> mention of focussing accuracy.
As do I.
> However, I point out that with very few exceptions, Gary's tests showed
> clearly that the OM2000 and the OM 4Ti delivered sharper images than the OM1
> with or without mirror lock-up, and any other OM body. Lenses on the bodies
> with pre-fire aperture stopdown and mirror lift WITH the Bogen long les
> support delivered even sharper images as I recall (without checking again
> tonight).
That has been my reading of the data, as well. Gary's tests have been and
continue to be a unique resource for
Zuikophiles, something no other camera brand has. And he did another great
service in bringing forward publicly the
aperture stop down mechanism vibration issues.
Nevertheless, some of his choices of methodology tend to exacerbate that issue
and other vibration issues.
1. He consciously decided not to try 'wetware' damping, holding the camera in
his hands and pressing down somewhat, as
not consistently repeatable. This is one of the constant dilemmas of human
interface testing. Does one test in a way
that is scientifically repeatable and consistent, but not representative of
most real world use - or test in a way more
like actual use, but subject to more variation?
2. He chose, for reasons I don't recall or never knew, although it may again be
repeatability, not to do any tests with
sand, bean, shot, etc. bags draped across camera and lens. Anecdotal evidence
here suggests that a nice heavy, 'dead'
bag is more effective than the Bogen support he tried.
3. He chose to use heavy, but very rigid tripods, aluminum, if I recall
correctly, on very hard surfaces. In some cases,
for long teles, I think, he actually melted the tripod feet into the ice of the
rink he was using for the shots.
So now do a little experiment. Take a piece of metal, press it firmly against
something hard and rigid, using something
hard, and tap it with another piece of metal. Now hold the same metal in your
hand, press it against your leg and tap it
again. His set-up really invited augmented sympathetic vibrations.
Take a carbon fiber tripod, which he didn't have available at the time, rest it
on proper rubber damping pads, and I'll
bet the results of a retest would be quite different. Add a 5 lb. bag of coated
lead birdshot draped across camera and
lens and the problem will disappear.
So a through reading of his work leads not to the conclusion that these
camera/lens combos are no good, but to the
conclusion that they require appropriate technique to give optimal results.
Gary later said that his tests had not shown the actual optical capabilities of
the really long lenses. He found that
with careful, through vibration control technique, they proved to be much
sharper than his tests had indicated. This
went beyond simple aperture mechanism vibration.
> When it comes to the market test of image acceptability, less than a full
> letter grade difference with a similar image made using a camera system which
> does not have this handicap, in all probability will be sufficient to ensure
> that the lesser quality image does not get used.
This seems to me to be a conclusion that can't be meaningfully drawn without
seeing actual test shots.
Moose
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