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Schneider Xenon-E 50 mm f/2.2 tested

 
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enricosavazzi



Joined: 21 Nov 2009
Posts: 872
Location: Stockholm, Sweden

PostPosted: Sat Dec 23, 2017 1:18 pm    Post subject: Schneider Xenon-E 50 mm f/2.2 tested Reply with quote

This lens was discussed some time ago at http://www.photomacrography.net/forum/viewtopic.php?t=30940&postdays=0&postorder=asc&start=0 . Opinions of this lens were not high when reversed and used in photomacrography at relatively low enlargement.

My tests at 2x and 3x reversed on Micro 4/3 format essentially confirm these findings. In addition, since Schneider states that this lens (in forward orientation) can be focused up to infinity, I tested it also reversed on tube lenses (50, 100 and 200 mm). It performs moderately better as infinite conjugate at 2x and 4x than as finite, but vignettes at 1x. Albeit, the improvement is still not enough to earn a recommendation for using this lens.

http://www.savazzi.net/photography/schneider_xenon_emerald_50.html

Season's greetings.
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Lou Jost



Joined: 04 Sep 2015
Posts: 1888
Location: Ecuador

PostPosted: Sat Dec 23, 2017 3:55 pm    Post subject: Reply with quote

Well, that's a surprisingly bad lens for a Schneider. But I found it interesting that the lens did better when coupled with a tube lens than when reversed by itself. At these low magnifications, that should be true even for a perfect lens optimized for infinity (because for a given aperture f on the prime lens, the effective aperture of the coupled pair is significantly lower than the effective aperture of the reversed prime lens by itself at the same magnification). This test shows that this may also be true of a bad lens!
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RobertOToole



Joined: 17 Jan 2013
Posts: 486
Location: United States

PostPosted: Sat Dec 23, 2017 7:53 pm    Post subject: Reply with quote

Thanks for sharing the info Enrico. Very interesting!

I do remember seeing that lens for sale on Ebay and the thread, you posted the link. I was hoping someone would test it more throughly one day.

I remember the auction, I sent the seller a low-ball offer and they agreed but before I could press the pay button all the lenses sold out. Looking at it now I am glad I didn't get a chance to buy one.

Robert
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rjlittlefield
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Joined: 01 Aug 2006
Posts: 18355
Location: Richland, Washington State, USA

PostPosted: Sat Dec 23, 2017 9:31 pm    Post subject: Reply with quote

Lou Jost wrote:
At these low magnifications, that should be true even for a perfect lens optimized for infinity (because for a given aperture f on the prime lens, the effective aperture of the coupled pair is significantly lower than the effective aperture of the reversed prime lens by itself at the same magnification).

I assume you're thinking about diffraction, but in this situation I doubt that diffraction is the main issue. More likely it's a matter that in dragging the lens too far away from its design point, significant aberrations get introduced. A perfect lens optimized for infinity will certainly not be optimized for use at 2-3X, reversed on empty extension. Even at image center, spherical aberration can cut contrast pretty badly. Away from image center there's a host of other possibilities.

See http://www.photomacrography.net/forum/viewtopic.php?p=102943#102943 for results of one particular 55mm f/1.8 operated at 2.45X, reversed on extension versus reversed in front of a 135mm rear lens. Big differences in the corners for that test, in favor of the two-lens combo.

--Rik
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Lou Jost



Joined: 04 Sep 2015
Posts: 1888
Location: Ecuador

PostPosted: Tue Jan 02, 2018 7:47 pm    Post subject: Reply with quote

Sorry, I missed this when you wrote it, Rik. Yes, I was thinking of diffraction primarily. That's an especially important difference between the two techniques at low m. But for any m, as you say, coupled lenses optimized for infinity have the advantage that they are being used more or less at their design point.
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