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Contax Zeiss Lens Test pages

D

davidfung

Hi. I have been surfing around the net looking for info for CZ lenses. Obviously, there is the MTF data from Zeiss, and there is the ubiquitous photodo. Has anyone checked out the following site:

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Anyone know how reliable the data is? By looking through it, it seems to conform to the relative perceptions of other Contax users and the published Zeiss data. However, it also includes some interesting information such as real aperture sizes, and 'mtf type' results for all apertures, rather than just wide open and two stops down. The down side is that it only provides center, edge and average.

Any other sites out there with such info?
 
S

singlo

Active Member
Hi David,
Check out these two sites but don't believe everything Photodo rates! AltriZeiss is quite
good. It shows the Zeiss MTF of out-of-production Zeiss lenses.

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Photodo used to publish their own MTF curves and I noted they were very different from the Zeiss curves. It is hard to tell the reliablity of Photodo tests. They do have quite a few inconsistencies in their ratings and tell you nothing about their precise grading criteria.
 
dirk

dirk

CI-Founder
... I would be very cautious with photodo MTF results.

1. Just the fact that they have access to some technical equipment to measure MTF curves does not mean that they know how to use it properly.

2. Photodo gives a totally different weighting for center and corner performance. So you actualy can not take just the numbers without looking in the details pages how they get calculated.

3. Even if you read the different calculation ex&les it does not help a lot. Some lenses are designed to perform specifically better in the center than in the corners. Or at closer distance and not at infinity. Or fully open and not at 5.5

So a general weighting for center or corner performance or certain lp/mm fails here.
 
M

mikel

Sing,

Bob Atkins in that article is talking about so-called "lens tests" that are mostly published in all sorts of magazines. It doesn't apply to Zeiss themselves. It's even funny that he actually mentions photozone. Ratings on photozone are collected from users. You can submit your own rating there. Needless to say, such "data" is purely empirical and thus it's funny that he mentions it as a good compilation of lens test results. There are technically only two companies out there that provide truly scientifically-based performance test results - Zeiss and Leica.
Photodo used to do MTF tests as well, and since in their case it was a purely enthusiastic work, they should be taken with grain of salt. However, since for the most part they nearly match results that are published by Zeiss, at least it means that their testing methods are pretty consistent. However, it also means that they have any meaning only within photodo. You can't compare ratings given by photodo and then some other place. Furthermore, since for the most part you never know when specific test was performed, it also means that you don't actually know whether specific Canon lens tested matches whatever is in production at the moment. Not to mention huge variations in quality of lenses coming off the production line at Canon, Nikon, Minolta and even Pentax. So, for the most part all these lens reviews and tests are quite useless. Unless there is an absolute consensus among users that the lens is worth its money.

Mike.
 
S

singlo

Active Member
hi Mike,
I fully agree with you.I have lots of faith with Zeiss MTF results; otherwise I wouldn't become a Zeiss fetishist! I don't trust Photodo,
individual DIY lens tests,and other independant
tests. Canon MTF graphs are computer simulated
results and they only represent the ideal predicted values. If you check them carefully,they are too good to be true!
 
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