Hi--

>> >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"...

>Thank you for your thoughtful and informative response. I have accessed
>your lens evaluations many times, and have found it both useful and
>informative.

Thanks for the comment - I thought you probably had seen it, but I wanted to drop in the reference for others...;-)

>There are of course lens-to-lens variations, and I can only address the
>two that I own.

A good point not as generally understood as it could be...

>I test all lenses using the old Modern Photography
>Magazine test kit and procedures. Many people dispute the value of
>such resolution/constrast tests, but I have always believed that if the
>lens cannot deliver sufficient lines per millemeter, whatever else it
>does is compromised. To be sure, lpm is not the only test of quality for
>a lens, but it is a necessary but not sufficient condition for lens
>quality.

I object to them due to the fact that they test at only one (possibly irrelevant) focus distance - and unless carefully done, can be quite misleading. Also, there are good examples of lenses that do not test well, but appear quite sharp...

>To standardize images and results, the procedures call for varying target
>distance by focal length. The 50mm lens is tested about 8+ feet. The
>tests were conducted using both B&W and chrome films, and were consistant
>over several tests and retests. Incidently, chrome film will almost
>always be used with the lenses.

Sounds like you have done this work in a way that would produce meaningful results.

>I should also tell you that I bought the 50/1.2 for my second trip to
>Egypt and a rematch in the barely lit tombs where flash and tripod are
>not allowed. I will be using Kodak 320T pushed to 640. The last time I
>was there, using my 50/1.4 shooting speeds ranged from 1/30 down to 1/8
>and occasionally even 1/4 shooting with my 50/1.4 and 35/2 lenses (I
>have replaced my 35/2 with a 35/1.4). I figured the extra 1/2 stop of
>the 1.2 might be critical, although I agree the actual light
>transmissions [T-Stop] of the two lenses might decrease the differences
>to less than 1/2 stop. I will recheck this using a camera with an analog
>meter (FE2).

Surprising results... - I would select for other reasons...

>The lpm for the 50/1.2 was the same at both 1.2 annd 4 (which I find a
>bit puzzling), and were slightly less than the 50/1.4 at 1.4 at the
>center. However, contrast was noticeably better with the 50/1.4.

This surprises me - I have found that the many 1.4's I have checked have a "filling haze" at f1.4, gone by f2 - the f1.2 doesn't, and therefore has considerably greater brilliance and feeling of contrast at f1.2-1.4 than
the f1.4. I am not at all surprised by having the same performance at f1.2 and f1.4 - very close together apertures...

>By f2
>there were both substantially better than wide open and generally equal.
>Despite using a focusing magnifier, the 50/1.2 seemed to do as well or
>even better at the corners than at the center (anomaly?), while the
>50/1.4 showed the normal slightly lower readings at the corners. I will
>re-evaluate since with the improved corner performance of the 50/1.2, it
>may be that overall even my sample of the 50/1.2 it is better than
>my sample of the 50/1.4, per your assessment.

Hmmm...;-) I would wonder if the center were worse than the corners... (field curvature combined with slightly inaccurate center focus...?).

>I think the whole thing comes down to whether under the conditions I am
>going to use the lens whether the 1/2 stop will give me any better
>results because of reduced camera shake, as compared to the very slightly
>reduced image quality the lens can deliver wide open. A number of the
>images previously shot wide open at 1.4 were soft, but that could be due
>to having to resort to 1.4 due to excessively slow shutter speeds, with
>the slow shutter speeds causing the softness. I just do not know.

I would try both with the film you will use, at the distances you will use, at f1.4 with real subjects and compare... I sold my f1.4, since the f1.2 beat it for what I wanted to use it for, and the compact f1.8 beat both for what I wanted to use that one for...

>Anyhow, I am rambling. This is not an end-of-the-world decision, but one
>that is important to me and is the kind of problem that makes the
>technical/equipment side of photography fun for me.

Ah, yes..., ..., ...... ;-), ;-), ;-)