On Sun, 15 Dec 2002 19:53:14 +0100, "Niels J. Larsen"
>"Neuman - Ruether"
>news:3dfbabd6.17039293@newsstand.cit.cornell.edu...
>> Little-reported, but lens performance is often very
>> distance-sensitive, and some lenses (particularly
>> "speed" lenses without "close-range correction",
>> like the 50mm f1.4, and asymmetrical designs, like
>> "retrofocus" wide-angles, "telephoto" long lenses,
>> and zooms) do not perform the same way even over
>> their normal focus range, let alone when they are
>> forced to focus closer... There are some examples
>> at www.David-Ruether-Photography.com/slemn.html, where poor
>> close (or distant...) performance relative to other
>> distances is noted.
>What it says about the 80-200mm is : "performance under about 8' at 200mm
>declines and becomes poor at minimum focus at wide stops (both conditions
>together) - otherwise this lens is wonderful even wide open;"
>
>To me this does NOT indicate that it should be a bad performer in macro
>photography, since (according to what I've read) you will need to use the
>narrow stops to achieve any useful DOF.
>Ofcourse it says that performance under 8' declines at 200mm, but I guess I
>could just use it at f.x. 150mm ?
It is not a "sudden" event, this loss of image quality...
You will see some of it at 150mm, and at 200mm stopped down
some. And more as you focus under 8' - "macro" work will
have you focusing WELL under 8' at the long end, giving very
poor results with tubes. If you plan on using smaller stops
(needed with tubes and achromats, anyway, for good
sharpness...), the subject AND camera cannot be moving - a
difficult thing to achieve (windless days, using a GOOD
tripod MAY do it...). Using a high shutter speed allows you
to get around this, but at small stops with available light,
this forces the use of fast film, itself an image-quality
limiter (at least with slide film...). TTL flash avoids both
most exposure-figuring problems and motion-problems...
>Regarding the 50mm I don't see anything at all that should indicate bad
>macro performance, sorry.
There is nothing there - it is assumed that people
know that fast lenses, asymetrical lenses, etc. (without
CRC) generally perform poorly outside their design focus
ranges (and sometimes even within - which is what I do
mention at www.David-Ruether-Photography.com/slemn.html).
>> If you use TTL flash for illumination, ambient
>> metering ability is not important... For high-
>> magnification work with moving subjects, flash
>> may be the only practical light source... (See
>> www.David-Ruether-Photography.com/phun.html, "Bugs" for
>> some examples of both flash and available-light
>> macro work with insects...)
>I see your point, but what if I just want to utilize natural or other forms
>of ambient lighting ?
Worth a try - but you will soon be trying to use very wide
stops (not necessarily a bad thing, but generally only lenses
specifically designed for high-quality macro work
are sharp enough to use at wide stops for macro work...).