rscheffler
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pdmphoto wrote:
Voigtlander came out with an emount version of the lens, but that does not mean it was optimized for the Sony thick cover glass. In fact, your sample data suggests that no change was made.
Based on a few tests I saw last year, it seemed the M-mount version performed slightly better adapted to stock Sony cameras than on Leica M digital, which would lead me to believe it's already designed to account for this factor. It could be that the optimization is a compromise somewhere between best performance on Sony vs. Leica. I.e. for a 1.5mm cover glass rather than 1mm for Leica or 2mm for Sony. But this is just a guess.
I had a re-look at my 15III tests done on Leica M240 and my results are closer to Fred's than Choppy's. By no means are any of my results as good as Choppy's in the image periphery for far distance images, but corners/edges do look good with near distance objects in infinity scenes. This leads me to believe there might be a touch of field curvature (towards the camera) at play with this lens on Leica M digital cameras. My copy also loses a touch of resolution in the left mid zone area, implying it might have a centering issue (though could maybe be camera mount related?), whereas my 15vII is OK in this region in side-by-side tests.
rscheffler wrote:
The cynical side of me thinks this is one reason Cosina does not publish MTFs for Voigtlander lenses.... It leaves individual lens owners somewhat in the dark in respect to a baseline level of expected performance, therefore each of us is more likely to accept a given lens's out of the box performance.
My impression about Voigtlander lenses has also been that they're somewhere between Samyang and Zeiss in respect to build quality and copy variation. The latest Voigtlander designs seem better and much more consistent in this regard, perhaps a benefit of their collaboration with Zeiss in building many of the Zeiss Z* lenses... but if you look at some of their older designs, the discussion happening here isn't anything new. For example, the 21/4 rangefinder lens is a rather old one and a case of copy variation lottery. It's possible to get a pretty good one, but requires testing multiple copies.
With the 15III it probably boils down to whether or not you can live with sub-par extreme corner performance most of the time as a tradeoff against other points in favor of the lens, such as its price, size, etc.
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Fred Miranda wrote:
Ron,
Yesterday I would agree with you but today I totally changed my mind about this lens. It took me 4 copies to see how well this lens can perform. I've been testing Guy's lens today and the results surprised me.
His lens has high resolution and contrast from center to the very corners even wide open (f/4.5).
Sweet-spot is really f/5.6 with a bump in micro-contrast throughout the entire frame. There is no detectable field curvature and that is really surprising for such wide angle lens.
The other 3 copies I tested (Including the new E-mount) were terrible at the very corners. So much astigmatism and low contrast. I was always vocal about this. But if Guy's lens is representative of how this lens really performs, I definitely have been testing defective lenses until now. It's perplexing that my bad copies are centered. This is something I have not seeing before. Either there is copy variation or I'm very unlucky. 
It competes neck to neck with my Distagon 15/2.8 at f/5.6 and f/8.
There are some issues though. High vignetting even at f/5.6. Lateral CA is also an issue at the corners and stopping down does not help at all. I consider vignetting and CA something minor though as it can be fixed with LR's custom profile for it but it's a negative for sure.
There are so many positives. Incredible resolution center to corner even wide open. Strong flare resistance and beautiful sunstar (subjective). The sunstar is similar to the Loxias and I particularly love it. It is strong with a nice shape even at f/8. Gotta love the 10-blade aperture.
I will post more crops tonight or tomorrow and update this thread. I got some better light here in San Clemente. This lens is a must buy.
Now, I have not seen a good E-mount version yet. The one I received is definitely a lemon and it's going back. I hope there are good copies out there because I want one!
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Fred, I'm looking forward to how your replacement copy performs. At the moment my cynicism leads me to believe that Choppy is an exception and that the majority of the 15vIII copies land somewhere between it and yours.
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