I'll repeat what I said once more. In reviewing most of Gary's tests
through 135mm I could find no definitive support for improved results
with mirror/aperture pre-fire over OM-1 mirror lockup. By that I mean
results worse by one full letter grade or more. If you do find it it's
likely that the test is of a different lens. In fact most tests are of
different lenses and simply not comparable.
This is tedious stuff and I haven't gone beyond 135mm where I'd expect
to find more vibration related problems. But up to 135mm I just don't
agree there's a real problem.
Chuck Norcutt
Moose wrote:
> 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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