Hi--

>>>Regarding the advantages or otherwise of using a 2X on a good
>>>telephoto: in my experience, it depends on the quality of the doubler.
>>>I did some tests a year or so ago, photographing the classified ads
>>>from the local newspaper, filling the frame top to bottom, with a
>>>Nikon AF 180 with and without a) a Tamron 2X 7-element doubler and
>>>b) with a Nikon TC201, on Delta 100 film.
>> [rest of long, excellent post deleted for space reasons, alas....]
>>
>>Wow! Nice post! I appreciate it when people take the time to actually
>>try something (instead of just quoting material someone else has
>>written, or expressing an unfounded opinion...), and then present the
>>results. I would note that: Lens performance can change radically with
>>focused distance (something often overlooked when chart-testing), and
>>close-focus performance at wider apertures is often relatively poor in
>>otherwise excellent lenses (the 180 AF, 85mm f1.8 AF, and 85mm f1.4 MF
>>Nikkors [and the macros] are unusually free of this problem among the
>>short/medium Nikkor teles); I have found the Vivitar 2X Macro
>>Converter to be the approximate optical equal of the Nikkor TC201;
>>I was not very impressed with the Tamron 500mm mirror either, but
>>the older-style Nikkor f8 mirror is excellent (except near closest
>>focus distance).

>Thanks for your reply. I'd been wondering about the
>close-focus/long-focus issue ever since I tested my 105 AF Micro (Nikkor)
>at "normal" chart distance (about 9 feet) and at about 1:3 macro focusing
>on one of the sections of the chart; I found a lot more corner fall-off
>with that lens at macro ranges, not noticeable at "normal" distances --
>consistent with what Moose Petersen says in his Nikon System book about
>the 105 not being a flat-field lens (unlike the 60 Micro), which seems to
>come into play only at close focusing. Otherwise it's a great lens. I
>also have been quite pleased both with my 180 AF and my 85 AF.

Hmmmm, I have REAL doubts about the 105 AF M not being flat-field! The
AF is sharper near 1:2 than the 105 MF (though the MF has some advantages
near infinity) at wide apertures. The AF should be very sharp to the corners
at 1:3 by f5.6, and quite good even wide-open, if not defective. Correct alignment/focus of a flat subject when close up is VERY difficult (it is hard
enough at much greater distances), so I generally check close performance
with the flat subject tilted so that a line of sharp focus joins diagonally
opposite corners (this minimizes focus error effects, and if the subject is flat, and the line of focus is straight, the lens is shown to have no field curvature). Testing is not as simple as it appears (though you have short
tele Nikkors that have good uniformity of performance with varying distance -
the 85 f2, 105 f2.5 and 1.8, 135 f2.8, 180 f2.8 non-AF have very noticeable
problems near minimum focus, and the 135mm f2 MF is terrible at minimum focus,
though really excellent at infinity at f2, as are the others wide-open),
which is why I sometimes rant-and-rail about chart testing (but do I get
around to finishing my article on lens testing?!?!).

>I've heard good things about the Nikon 500 mirror, but I'm wondering
>whether I'd be getting enough extra sharpness over my 300 f:4 + TC201
>combo to justify the expense (that combo converts to 600 f:8). I'm told I
>might get better results with the TC301, but I got the TC201 since it
>works both with the 300 and with the 180 (which I use a lot more on
>overseas travel, as it packs a lot easier in a camera bag, not to mention
>lower profile, less weight, etc.). Besides, at least here in Canada the
>TC301 costs about as much as the 500 mirror lens.

The older f8 500mm Nikkor is much better than the TC201 with the 300mm at
f4 (f8), I would think. The 300mm f4 was not very good on any converter
(I have 5 Nikon versions) I have tried, though acceptable on the TC14/B/C.

>The Tamron mirror was a dog -- I kept getting really fuzzy images, which I
>was attributing at first to slow shutter speed, then to vibrations on the
>tripod caused by the wind, then maybe to difficulty with focusing a dim
>image, but then I did the tests and found it was the lens. The Tamron
>converter was a disappointment too (I had the AF version); close
>examination of the test patterns on the chart revealed really severe
>astigmatism (sharpness differences from two to six intervals on the scale
>between right-angle orientations, differences varying with the aperature
>used on the lens); I've never seen astigmatism like that with any Nikkor
>optics I've ever tested.

But people on the 'net still rave about their El-Cheapo (though some aren't cheap!) Productions 14-586mm f2-34....;-) I have found a few off-branders
that are good, but the vast majority....... (Don't know if you have seen this:)

My "SUBJECTIVE Lens Evaluations (Mostly Nikkors)", version
5a, which includes a listing of all Nikon SLR lenses ever made (with a
subjective evaluation of many of them, a general description of Nikkor
lens performance characteristics by lens-type groups, and comments on
particular lenses when the general descriptions plus the subjective
evaluation numbers are not sufficient to describe performance),
can be found at these sites:

-- Jan-jaap Aue: (nice text format)
http://www.phys.rug.nl/mk/people/aue/nikon/david.html
-- Quang-Tuan Luong: (nice text format)
http://robotics.eecs.berkeley.edu/~qtluong/photography/35mm/
nikon-neuman.html
-- Niklas Nikitin: (nice table format)
http://www.cs.hks.se/~nicke/private/photo/lenstest/david.html

>If you're interested, I ran a lens testing workshop a few months ago for
>some of my colleagues at our photo club -- people brought Leica, Canon,
>Pentax, Minolta and Tamron optics for testing. I checked their results
>(same test procedure and film of course) against my equivalent Nikkor
>focal lengths. My Nikkors blew away everyone else's lenses consistently,
>except for a Leica 50mm f:2 which is the sharpest lens I've ever seen.
>The strangest findings were with a couple of Tamron zooms (I forget the
>focal lengths) which had severe pincushion distortion and whose corners
>were consistently much sharper than the centres, something I've never seen
>on any other lenses.

Pincushion on film, or in the finders? (Most new bodies have it in the
finders rather noticeably, and the finders show focus errors [if you can
focus at all] near the corners.) I compared a $3800 double-aspheric 35mm
f1.4 Leitz with the Nikkor 35mm f1.4 recently, and posted it. The Leitz
was mostly better than the Nikkor at apertures wider than f5.6, but nothing
like the price difference better - and it did show slight misalignment, and
soft corners, which were bettered by the 35mm PC and 35-105mm Nikkors I
threw in for reference.

>All of this of course is incidental to being able to take a decent photo,
>but especially for close-up work having a sharp lens sure helps.
>Ed Overstreet ak926@freenet.carleton.ca

Many on the 'net seem to disagree, but I think sharp, well aligned lenses
are the foundation upon which one proceeds to do photography - it's no fun
working around lens problems when taking pictures......
David Ruether