WoW. That is a big "erroneous" statement.
I tried the Zeiss 15mm and have somewhere a forgotten Nikkor 15/3.5
The universally known cream of the crop which is sitting pretty in it's leather sheath sleeping in my cabinet is the:
Leica R Super Elmarit 2.8 Asph (which in fact is a Schneider-Kreuznach)
Unfortunately, I don't use it much as I do not do landscape or architectural photography.
Big erroneous? Almost every site or measuring platform places the Zeiss as the pinnacle and doesn't mention the Leica (although that could be because so few people can afford Leica.)
I am grateful for any new information, so thanks for bringing this up. I did an online search for it, and it looks like a very expensive, discontinued lens. The price is still $6000-$7,000, despite its being discontinued, so I am sure it is a great lens.
I tried to look it up on LenScore, and couldnt find it. However, of the top 20 lenses at LenScore, Nikon made 9, Canon 6, Zeiss 3, and Leica only 2. (As far as Schneider-quality goes, compared to Zeiss-quality, the only 2 Schneider lenses measured were at the 28th and 30th positions, one a macro, the other a tilt-shift, respectively. Their best lenses may not be well-represented here though.)
While 2 50mm Leicas did occupy the top 10 area,
most of the Leica lenses were in the middle, to lower-middle level, including the Leica Super-Elmar-M 1:3.4/21mm ASPH, which not only had an unimpressive score (despite its expensive price), but was a few notches
down from its equivalent, the Zeiss Distagon T* 2.8/21 (which itself did not rank as high as the Zeiss Distagon T* 15mm f/2.
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In doing even more research, what I found interesting was that Zeiss actually refurbished its own 15mm to make the original ultra-wide for Leica, the 15 f/3.5, whereas Schneider made the f/2.8 15mm lens for Leica (as you mentioned). As for comparisons between this Schneider version and the Distagon T* 15mm
f/2.8 of my inquiry, the only semi-comparison I found came from
Fred Miranda's site, which said,
- 3) Carl Zeiss Distagon T* 15mm F3.5
An amazing accomplishment at this super wide angle that met a lot of challenges of the super wide angle lens. 1) The most resilient lens against CA that I ever tested only second to the Zeiss Mirotar 500mm F4.5. 2) It is superb against flares. 3) It is a very sharp lens and well distributed across the whole entire image. 4) The only negative down side which lead to some folks stay away from rectinlear lens is the 4% distortion. It very well built and has a built in filter turrret. Will work on any Canon 1 series camera with an adapter.
- 4) Leica Super-Elmar-R 15mm F3.5
This is the same lens that Carl Zeiss designed for Contax above. This lens will work on your Canon 1 series camera with an adapter since it is a Zeiss design thus the rear element is further away from the mirror. The one thing that I love about this lens more than the Contax version is that I have not come across one lens that has stiff focusing mechanism. However, the aperature opening is typical of Leitz and not Zeiss where the Contax Distagon 15mm F3.5 with wide open f stops yield the Ninja Star.
- 5) Leica Super-Elmarit-R 15mm F2.8
This is a very recent lens thus all of them comes with ROM. The production start in 2002 and it is by Schneider Optics. This lens pick up where Zeiss left off and corrected the 4% barrel distortion all the way down to 2% barrel distotion. Thus, it give us a very pleasing looks and for those that shy away from this focal length due to distortion will love this lens. The image is the sharpest super wide angle lens that I have ever seen especially in the center. It even beat the Zeiss 21mm F2.8 and is as sharp as the Leitz 60mm macro lens. However, on the edges it is a little soft compared against the standard Zeiss 21mm F2.8 but similar to the Zeiss Distagon/Super-Elmar-R 15mm F3.5 on the edges. Thus, this is a great accomplishment by Schneider. The only other thing is that the CA is not as well control as the Zeiss Distagon/Super-Elmar-R 15mm F3.5. This lens has a built in filter turret. It required mirror modification in order to work on Canon 1 series DSLRs since the mirror hisses the rear element housing.
Keep in mind, this compared the Leica Super-Elmarit-R 15mm f/2.8 against the Zeiss Distagon T* 15mm f/3.5 not Zeiss' improved f/2.8
From what I understand, while the Leica/Schneider f/2.8 is sharp, the newer Zeiss Distagon T* 15mm f/2.8 is sharper than the Zeiss 21mm also. Meanwhile, even the elder f/3.5 Zeiss has much better CA control than the Leica, as well as the best anti-flare resistance of any ultra-wide. So it looks like a trade-off. By all accounts, the same superior rendering qualities were passed to Zeiss' f/2.8 upgrade, which improved barrel distortion and sharpness as well (the development of which came after the Super-Elmarit-R 15mm F2.8 was discontinued). And we haven't even discussed the Milvus, which likely has improvements also.
In closing, the only "universal" statements I have seen is that the Zeiss Distagon has superior color color rendering, CA control, and anti-flare control. However, I would be curious to learn of your sources (other lab results, or links) which definitively show the Leica R Super Elmarit 2.8 Asph to be measurably-superior in various important respects to the Zeiss Distagon T* 15mm f/2.8?
If not, is it possible that your "big erroneous" statement was itself erroneous, and merely your subjective opinion formed by not owning the Zeiss f/2.8 and not really using the Leica?
Thanks.