Archived posting to the Leica Users Group, 1996/03/11
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]In article <4i27ah$rso@newsstand.cit.cornell.edu>, rpn1@cornell.edu (Bob Neuman) writes: |> In article <4hvg3i$qfg@ccshst05.cs.uoguelph.ca>, gtoop@uoguelph.ca |> says... |> >Bob Neuman (rpn1@cornell.edu) 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 |>