johnchap@erols.com wrote in message <884364800.2126839814@dejanews.com>...

>I seldom use prime lenses, unless I need very fast glass. I currently
>have both the 50/1.2 (not the Noctilux) and 50/1.4, and am trying to
>decide which to keep. I have done resolution tests on both lenses and
>find that the 50/1.2 essentially does the same at 1.2 and 1.4 (is this
>normal that there was no apparent improvement by 1.4?), and that the
>50/1.4 has better contrast and slightly better resolution at 1.4. By f2
>they are both comparable; i.e. excellent. The 50/1.2 is larger and weighs
>almost 50% more than the 50/1.4.
>
>Given that when I will use the prime 50mm lens it will almost always be
>at f2 or faster, the question in my mind is whether the extra half stop
>in available speed of the 50/1.2, which I will use at least sometimes if
>it is available, is worth a slight loss in resolution in contrast.
>
>I would appreciate opinions from any professionals and really serious
>amateurs regarding my dilema, for whom photo sharpness is paramount. As
>a postscript, it is likely that under the lighting conditions for which I
>need this lens speed, I am probably already using very fast slide film
>(e.g. tungsten) perhaps pushed one stop that likely builds contrast and
>introduces grain that tends to camoflauge minor lens faults.

Hmmm, probably not a half stop faster with f1.2 vs. f1.4, and if you take
two frames under identical conditions on contrasty B&W negative (except
that both lenses are used wide open - with the same shutter speed), you
may be surprised to find in the contact sheet that there is VERY little
true speed difference between them. I find the f1.2 Nikkor a special-use
lens. It, like the f1.4, is distance-sensitive, though much more so. Used
at its optimum distance (roughly 8', give or take a lot...), the f1.2
will outperform the f1.4 wide open in both resolution and contrast over
the whole frame (and is quite good even in the corners), but used near
infinity focus, the edges at wide stops are soft. The f1.4 is very fine
over most of the frame by f2 through much of its focus range (though the
edges and corners are not crisp at f2). The f1.2 shows large coma effects
at wide stops near infinity focus. I keep mine for use in shooting people
inside, where the f1.2 is a great lens for wide open shooting from about
4 to 15 feet or so. For long distance shooting, use the f1.4 or f1.8 at
f2 or smaller stops... BTW, you may find my "SUBJECTIVE Lens Evaluations
(Mostly Nikkors)" interesting - on my web site, under "I babble"...
--
David Ruether
http://www.fcinet.com/ruether
ruether@fcinet.com