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Re: [OM] Telephoto lens tests

Subject: Re: [OM] Telephoto lens tests
From: bj@xxxxxxxxxxxxxxx
Date: Sat, 31 Dec 2016 11:33:47 +1300
 

Brief response; Moose wrote; 

Sharpness improves at ƒ/4, and the
uneven sharpness seen above 100mm settles down. Below that, sharpness
registers at 1 unit, which is about as sharp as we can measure. Optimal
across-the-frame sharpness is obtained at ƒ/4, 70mm. Diffraction
limiting starts to set in at ƒ/16, but even here you're not exceeding 2
units on the blur scale. Even at its worst, ƒ/22 at 200mm, you're at 3
units on the scale. Superior results."
<http://www.imaging-resource.com/lenses/olympus/50-200mm-f2.8-3.5-zuiko-digital/review/
[1]> 

2. You used FF thinking, doing the test @ f8. Note in the above
test that the sharpest aperture for this lens was f4. Optimal aperture
for 4/3 is generally f4-5.6. F8 is still quite useful, but generally not
quite sharpest. 

3. My own experience is that at least µ4/3 lenses out
resolve the sensors. I expect this to be true of top line 4/3 lenses, as
well. I have taken otherwise identical test shots with the E-M5 II at
both the normal resolution and with the ~50 MP HR Mode. The considerably
greater detail in the HR images is proof that the limit @ 16 MP is in
the sensor, not the lenses. 

By using the 10 MP E-3, with roughly 25%
less resolution than your E-M5, you further limit the performance you
experience.

4. I've said it before, and will probably do so again,
shooting JPEGs further limits resolution compared to optimal Raw shots
properly converted. I've gone into the details before. 

I just don't
see the point in making a telephoto lens extending to 200mm or whatever
and having the resolution at the max distance to be sub-optimal. Weird
thinking. 

Especially having the sweet spot at 70mm ??? What were they
thinking. 

When it stops raining I will do the tests again for this
lens at f/4. The blooms are still there. However I note that I would
usually go for f/8 or thereabouts. 

The minuscule DOF available at f/
2.8, 4 etc would not give the kind of detail, over the whole body of a
bird, that I would desire. 
In comparisons of images taken with the E M5
and my E-3, if I'm careful with the photography,there's little
observable difference in resolution. 

There IS a big difference in
weight to lug around though. 

A major reason for using the E-3 instead
of the M5, with manual focus lenses, is that the real mirror of the E-3
makes eyeball focussing heaps easier. 

By using jpegs versus anything
else, and not fiddling with the images myself, I reduced the
experimental variability. Each test image was given the same treatment,
by my criteria. 

I don't have a RAW converter yet. But exposure
features such as colour intensity, brightness etc were not under test.
For the purposes of the trial I ignored them. 

I would also have tested
the Zuiko 500mm mirror lens which has worked wonderfully well for me on
the E-1 However, mine was lost in the house fire. On the + side, I just
won one on eBay in HongKong and it should be here soon. 

I do envy the
kinds of result that people with canyon gear get with wildlife such as
albatrosses on the wing ( LARGE birds) etc. Sometimes hand-held too.


Cheers, (half way through the last day of 2016) Brian


Links:
------
[1]
http://www.imaging-resource.com/lenses/olympus/50-200mm-f2.8-3.5-zuiko-digital/review/
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