On 7/5/2018 10:31 AM, Jan Steinman wrote:
From: Ken Norton <ken@xxxxxxxxxxx>
Heard a bald eagle this morning.
When we first moved here, it was, "Oh look! There's an eagle! How wonderful!"
Then they began eating our chickens. Now, it's "DAMN! There's another f***ing
eagle!"
Obligatory on-topic stuff: eagles through multiple lenses, a Classic Hit:
http://www.bytesmiths.com/OM_Tele/
There were several things about this test/post that bothered me. Now, you've
posted it again. :-)
There are a few things I know.
One is what a shot with a decent lens @ 300-400 mm on a 4/3 sensor looks like. I've taken over 9,500 over the last 6
years. These don't look right.
Another is that big birds in tall trees sway from breezes and their movements also move the branches. For several years,
we had Redtail Hawks nesting across the street. Much closer than those Eagles and around for weeks at a time. Yet, I had
real trouble getting good shots of them. Between the relatively slow speeds of films and long lenses, the constant
swaying of the trees and movement of the birds, motion blurring was a constant problem. (I think now I underestimated
atmosphere effects back then.)
Third, I know that atmospheric movement has a greater effect, at closer distances, than one might imagine. I found a
subject that doesn't wave around in the breeze, and I believe is quite a bit closer than your Eagles. Now, look what's
happening in the air between lens and subject! <https://vimeo.com/279563550>
Nice day, air temp between 65° and 70° F. Can you imagine getting a really sharp photo through that? Even with v. high
shutter speed, notice that details are distorted, waving around. It looks to me as though your subject distance is more
than twice as great - and many shutter speeds quite slow.
I suspect this test is so compromised by these factors as to be useless in
evaluating differences between the lenses.
As Ctein said when testing my PLeica 100-400, to see if he wanted to rent one
for a project:
"Hard to say how good the lens is by any objective measure. It's insanely hard to critically test an optic like that.
Stuff that's far enough away that depth of field isn't a problem, there are atmospheric ripples and distortions to deal
with at the 400 mm end. Stuff that's close enough that that's not a problem, I have to compare multiple frames made with
the same aperture where I shift to the camera to move the point of focus to different parts of the field of view. It's a
pain and not terribly precise."
I know I should put my test photos where my mouth is. One nice thing about where we live is that there aren't many
suitable targets to do something like what you did with the Eagles. There's a power pole with transformer at about 40 m,
if I get out the really tall tripod, or stand in the street. :-) OK, did that.
<http://zone-10.com/tope2/main.php?g2_itemId=22966>
Ordinarily, I use HR mode for lens tests, but that would have been wasted
effort here.
I went ahead, in spite of the air movement, I suppose because this isn't an atypical sort of shot for me, of birds,
etc., as opposed to test targets.
Here's a comparison of lenses at 300 mm.
<http://www.moosemystic.net/Gallery/tech/Lenses/300mmLenses/300mm.htm>
Notice that shapes change slightly; that's refraction through air cells. So don't pay much attention to tiny apparent
differences in resolution. Also note how much the trees in the background move between shots. This was not a windy day,
only v. light breezes.
As I expected, the OM 300/4.5 came in last, although not by a lot. It's optimized for a much larger image circle, so
we're throwing away a lot of the designers' efforts. It was also never the sharpest tack in the OM box, good, not great.
I suspect that's in part because of the overall successful effort to make a small, light long tele. (Well, long then.)
When I compared the two OM 200 mm lenses to the older design Nikkor-Q 200/4, the Nikkor whupped 'em, center and edge.
It's also much larger and heavier. I believe the N was designed for optimal performance, while the Os were compromises
between size/weight and optical performance.
This test was also of interest to me as the Panny 100-300/4-5.6 II just arrived yesterday. I couldn't find a good
comparison of the Oly 75-300 to even the 100-300 Mk. I, and the Mk. II is too new for tests to be available. Looks like
a good choice, as this copy Panny nicely beats my old Oly, in the center, at the long end. That's where many subjects
are . . .
Why, other than rampant G.A.S.? I wanted a longer lens with OIS to use in a smaller kit with GM5. And I ran across a
used one - already. Adorama rated it EX-, but I can't find anything not like new; doesn't even look like it was mounted
on a body. The box shows some wear, though. ;-) The Oly goes in the sale bucket. I kept it as back-up to the PLeica
100-400 on trips like Bhutan.
OTOH, standard practice, to compare apples to apples, is to test all lenses@ 1:40 repro ratio,which is (or was?) the
target focal distance for lens design optimization. As it happens, an otherwise annoying quirk of our house layout
allows me to do indoor tests @ 1:40 for up to 400 mm lenses. And I prefer those boring test target shots for evaluating
lenses, but I can't do the longer mirror lenses that way.
AHA!! I put off clicking "Send" and nosed around. I just found some HR test shots of resolution targets with OM 300/4.5,
500/8 and PL 100-400 @ 300 and 400 mm. More stuff to do.
Resolute Moose
--
What if the Hokey Pokey *IS* what it's all about?
--
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