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virtualrain
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Re: Fred's Decentering Test




stevei wrote:
I\'m starting to understand that the hard part isn\'t testing a lens, it\'s trying to estimate what percentage of lenses sold are better than the one you\'ve just tested. I.e. they\'re pretty much all imperfect to some extent, so you\'ve got two things to try to work out:

1. Where does the lens you\'ve just tested sit in the range of all lenses that leave the factory? Is it in the worst 10%, the best 50%, the best 20% etc. As far as I can tell, it\'s extremely hard to estimate this, though we can perhaps get some idea by sharing test shots on a forum such as this one.

2. What standard of lens is it reasonable to expect? Is it reasonable to return lenses until you get a \"best 50%\" copy? Until you get a \"best 10%\" copy?

Then you\'ve got the added problem of lenses having different defects. I\'ve had 3 35/2.8s, and the sharpest one was the most decentered. So now, if I get a lens that is very sharp, I\'m more inclined to forgive minor defects in other aspects, as I know that if I get another one without those minor defects, it might be less sharp over most of the frame. Would you rather have a decentered lens that is super sharp except for one less sharp corner, or a perfectly centered lens where every corner is only as good as the weakest corner of the decentered lens?

You can tell I\'ve just bought an imperfect Batis 18 and am trying to decide whether exchanging it is likely to make things better or worse.........


This is a good idea.

In my case, my first Batis 85 was slightly less sharp on the left but was very sharp on center and the right half. I exchanged that with Zeiss that was sharper along the top than the bottom. They sent me another replacement that had one really bad corner but three decently sharp corners. Realizing a perfect copy is likely impossible, I\'ve opted to keep the one that\'s sharp across the top as I tend to use it for candid street shots so having people\'s faces sharpest is better.



Aug 05, 2016 at 08:54 AM





  Previous versions of virtualrain's message #13669805 « Fred's Decentering Test »

 




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