Hey Moose, wasn't ignoring your "scary video;" was away at spouse's 40th high
school reunion. (Yawn. Took a bunch of photo gear to amuse myself. Everyone
there had phone cams, and I did not want to be presumptuous about shooting
people I had never met. It was 104 degrees outside in the central Washington
desert, and the hotel room air conditioner could barely keep it in the 80s.
Spent my time playing with LensFun to try to get the OM 21/2 CA to behave on
micro 4/3rds.)
> From: Moose <olymoose@xxxxxxxxx>
>
> Did you view my video? Look again, paying attention to how the amount of
> degradation
> varies quite a bit as the air moves.
Looked at your scary movie. Didn't look all that scary. I'll bet any given
frame of the vid was fairly sharp. My eagles were shot at a fairly high shutter
speed (between 1/60th and 1/1000th), but of course, a faster shutter at larger
apertures. So that might explain some of the results at smaller apertures.
Also, the eagles were shot in fairly stable air, not near large heat-absorbing
surfaces, which tend to cause large temperature discontinuities over small
distances.
That said, of course this, like all "tests" was flawed in many ways, EXCEPT
one: it showed fairly well how shooting that particular subject under those
particular conditions worked or didn't work with the various lenses. Of course
a certain amount was actually "testing" the subject and the conditions. I just
object to calling it a worthless test.
> In fact, if air movement didn't have such an effect, and assuming your copy
> of the Celestron is not a bad one, it should
> again win on sheer magnification. Reading the tea leaves of Modern's tests
> show it to likely have as good resolution, or
> better, as the Oly 500/8.
I don't accept Modern Photography as the be-all and end-all of lens testing.
I've read other reviews of mirror lenses that showed the opposite: that the
C-90 is quite a bit below the Zuiko Reflex.
> The old cant from folks like Norman Whatshisname, the chief tester at Modern
> Photography is that lenses were designed to
> perform best at 1:40. If that is true, then it should get worse, although it
> may be a very tiny amount.
Oh, well if Whatshisname says so, it must be true!
I really don't understand such a belief, not without some evidence to back it
up. Did Old Whatshisname cite individual lens designers who made that claim?
Certainly, particular lenses perform better at reproduction ratios of other
than 1:40, which would be inches away on fisheye or ultra-wide. And that rule
is clearly wrong for macro lenses.
I also fail to see why anyone would design a super-tele that was optimized for
less that super-tele use! Especially if they don't actually focus close enough
to achieve 1:40. :-) I suspect the "1:40 rule" was only for lenses between 28mm
and 135mm or so.
> It's a REAL EYE OPENER for anyone who shoots even modest distances with
> teles. That means outdoors is not suitable for evaluating lens IQ
There are as many ways of dealing with atmospherics as there is with camera
motion, or subject motion, for that matter.
#1: Don't shoot when there is a high lapse rate and unobscured sun. If the air
column is the standard lapse rate (about one degree Celsius per hundred metres
of elevation), and it is overcast, then you won't see *any* atmospheric
rippling, which is caused by refraction between moving air layers of different
temperature. This generally means overcast with little wind. I'd like to see
your vid repeated under such conditions, Moose!
> The only thing anyone is likely to see
> between them in web images or prints is the halo bokeh of the mirror lens.
Yea, sometimes it's a pain. But no, sometimes, it is invisible or unnoticeable,
particularly for low-bokeh subjects, which is essentially anything
super-tele-worthy. And sometimes, it is lovely, adding interest to an otherwise
bland subject.
So yea, you can say a screwdriver makes a lousy hammer, and you'd be right, of
course.
All I can say is I love what the OM 500/8 does for distant boats from a ferry.
In such a case, the cool water surface means you don't have temp-differential
diffraction, and the relative lack of both subject and camera motion means you
don't have to worry much about motion blur. And the light weight and short
length of the mirror lens makes it much more stable.
So maybe I'll test all those lenses again, this time shooting distant boats
from a ferry. :-)
Jan
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