[Leica] any Sony rx 1 users

[chris at chriscrawfordphoto.com (Chris Crawford)]

Paul,

I'm curious about decentering. How can you detect it by looking at the
photos the lens makes...what does decentering do to the image?

Thanks,

-- 
Chris Crawford
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On 1/8/13 12:24 AM, "Paul Roark" <roark.paul at gmail.com> wrote:

>Mark,
>
>I agree, in general, with what you are saying.  However, assembly
>costs of Cosina may be enough less that an equal optic can be made for
>less.  Also, Leica can command more for the same just because of the
>name.  So, there are differences in both the supply and demand sides
>of the equation that may sometimes modify the strict "you get what you
>pay for" formula, particularly if we are just looking at optical
>performance.
>
>I put a fair amount of weight on the published MTFs of the 2
>companies.  While the MTFs of Leica and Zeiss may not be exactly
>comparable, the main performance variances I've seen from either --
>actually only Zeiss -- appear to be due to de-centering and focus
>distance sensitivity.  Specifically, my Zeiss 50mm f/2 has off-axis
>performance that takes its f/4 performance way below what the MTF
>represented.  It is also clearly de-centered, and that may well
>account for the deviation from the published MTF.  I buy from
>retailers where I can send things back.  I did send 2 of the samples
>back.  After the third de-centered sample I gave up and decided for my
>uses and given the budget I had to spend at the time, I'd just accept
>an optic that was barely better than the Canon equivalents, and
>clearly not assembled with the perfection of the sample they tested
>for the published MTF.  (I have a sharp mountain ridge view from my
>back yard that easily detects a decentered optic.)
>
>Subsequently, I did purchase a Leica 50 f/1.4 ASPH, and it is the best
>1.4 I've used or tested.  However, consistent with it's MTF, I can see
>a dip in performance, particularly wide open, half way out from the
>center to the edge.  Also, the Zeiss f/2 is sharper in the center at
>f8.  So, the Leica is not a perfect optic by any means (and it's way
>heavier).  I might add that I've never had/tested a de-centered Leica
>lens, and the Leica MTF representations have been right-on all the
>time.
>
>The 18 ZM -- my other Zeiss disappointment -- is a retrofocus that is
>simply not good in the corners close up.  (My Rollei SL66 50 Distagon
>was terrible there also.)   It's a likely eBay item in the future.
>
>On the other hand, the ZM optics I have that are well
>assembled/centered, the Biogons, have relative performances -- Leica
>v. Zeiss v. MTFs -- that were very much predicted by the MTFs the 2
>companies publish.  The 35 f/2.8 Biogon image, in terms of sharpness,
>looks very much like that of the 28mm f/2.8 Elmarit ASPH I also have.
>On the other hand, the published MTF of the 35mm Summarit 2.5 is very
>unimpressive wide open -- sufficiently so that I am not interested.  I
>believe Leica here and appreciate their honesty.  I also believe
>Leica's MTF for its 35 f/2, and at f/2 it is not good enough to pay
>for given my usual landscape shooting.   So, the Zeiss simply seemed
>to have the best combination of price and performance for my uses at
>this focal length.  Same with the 21mm focal length.
>
>Down the road I may find that the Zeiss optics fall apart, whereas the
>Leica ones are far more robust; they do have that feel.  So, far,
>however, the Zeiss Biogons I have deliver performances that are right
>up with the very good Leica optics but at a lower price, and so far
>they have held up fine.
>
>So, I tend to pick the optics based on the MTF as well as price.  I
>don't expect magic from either (or any) company.
>
>For those interested, I've posted a Jpeg containing copies of the MTF
>charts of the optics I have and others of interest from Leica & Zeiss.
> See http://www.paulroark.com/BW-Info/Leica-Zeiss-MTF.jpg .
>
>Paul
>www.PaulRoark.com
>
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