In article <4hvg3i$qfg@ccshst05.cs.uoguelph.ca>, gtoop@uoguelph.ca says...
>Bob Neuman (d_ruether@hotmail.com) wrote:
>: I recently had a chance to check out a Leitz Rangefinder
>: Double Aspheric Horribly Expensive ($3800 when new) 35mm f1.4
>: lens, courtesy of Nick Silva (who kindly shot the tests to order
>: and supplied the film to me). I shot similar test film (B & W and
>: color) using a Nikkor 35mm f1.4 to attempt a comparison. Though the
>: Leitz lens remained in California and my 35mm f1.4 Nikkor remained
>: in New York, I have reasonable confidence that the results of this
>: long-distance comparison are reasonably valid. So, here is what I
>: found:
>SNIP
>Thanks, these test results were interesting! However, it seems worth >noting that B+H advertises the current 35 1.4 ASPH at $2 900, not
>$3 800. Perhaps that makes it only very expensive and thus a Double
>Aspheric Very Expensive or DAVE lens. (The current Nikon AIS lens is >$700).
Hmmm, mebbe ;-) The lens I compared with the Nikkor is different from
the current Leitz aspheric, and it may be better, the same, or worse
in performance than the current lens - I don't know.
>Also, it would help us all to know how your testing was carried
>out. What kind of magnification did you use when viewing your >pictures? People will sometimes pay a lot of money for a lens
>that is only visibly better when you enlarge it 16 or even 20 times.
I consider enlargement size mostly irrelevant after there is enough
to see the differences you are looking for. A lens that will make a
sharp 8x10 will also make a sharp 16x20, since the viewing distance
for the larger print is also increased. Also, many lenses do not
perform uniformly well in all parts of the frame, and even low magnification will reveal the problems of both the Nikkor and the
Leitz 35mm f1.4's in the corners - neither is really sharp in the far corners wider than about f5.6 (though neither is really terrible over most of the frame even at f1.4). To answer your question specifically,
a 10X magnifier was used directly on B & W and color negatives, and 6x9
prints were made from some of the B & W negatives.
>More importantly, did you simply shoot test charts or did you also
>photograph 3 dimensional objects? Leica claims that it engineers its
>lenses with the latter in mind and there certainly can be a signficant
>different between the way that a lens reproduces a test chart and the >way that it reproduces a 3 dimensional object.
That never made sense to me, much as I dislike the chart method of
lens checking. (ONE of these days, I will finish that article on simple methods of lens checking!) I used 3-D subjects, at infinity (I use 2
or 3 additional distances in a thorough lens check, but this long-distance comparison of two lenses was only really practical using infinity subjects.
>The results that you obtained were interesting and the posting was very
>useful: its value would increase if we knew more about how you got the
>results.
>Gary Toop
To tell you a bit more, the comparisons are made with the assumption that most good lenses perform well, and about equally, in the center
at f5.6. That reference level can then be used to judge the relative
quality of other parts of the frame, and the relative quality of other
lenses, without needing the "go-between" of chart numbers, especially
if the subject chosen is the same, or at least similar, for different
lenses. Also, since I am only looking for relative sharpness, identifying the source of problems (other than construction
misalignment, which can often be spotted using my methods), such as
astigmatism, coma, etc.) is not necessary - I am looking to answer
the question, "Is the lens useably sharp at the apertures I am interested in using, at the distances I will use the lens at, and
in the parts of the frame of interest for the purpose I have for the lens?" In 25 years or so of asking that question, I have become fairly
proficient at lens checking.
Hope This Helps