Interesting: weird de-centered Contax 45mm

[spiffariffic]

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I found a fairly inexpensive (or should I say "inexpensive") Leica C adapter, and grabbed an "Ugly" Contax 45mm from KEH. (Usually I can't find any appreciable issues with ugly lenses, but also usually they're not high-end medium format.) For $300 with a solid return policy, I thought: why not? And I could make sure my adapter worked at least.

And the lens did indeed work. Had some haze although it was mostly not noticeable, I might have kept it except… 

It has de-centering unlike any I've ever seen before. This is shot at f2.8, with the focus being on the mountain peak at approximately 500 ft away as the crow flies:

 

 

 

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Edited March 30, 2024 by spiffariffic

[spiffariffic]

f/4, focus on the ridge, probably about a mile away… if it weren't for the soft part of the ridge to the right, I'd probably keep this lens and use it for landscape. Who wouldn't want a freakishly deep depth of field? I'd barely have to stop down 😂 Alas, of course, there's a downside. 

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[adan]

I certainly wouldn't discount the possibility this is simply an "ugly" version of the lens, as you describe.

But the 45mm Distagon did not exactly have even performance across the frame, even when straight from the factory.

Here's a link to Zeiss's own technical brochure for that lens - and its MTF chart (resolution x contrast) is quite the snakepit. See 2nd page of the .pdf for the MTF graphs

https://www.zeiss.com/content/dam/consumer-products/downloads/historical-products/photography/contax-645/en/datasheet-zeiss-distagon-2845-en.pdf

Lots of astigmatism (divergent dashed and solid lines of the curves) - which means the sharpness will be variable according to the orientation of the lines in the scene details (straight out from the center, or at 90° to the center). And the lines bounce up and down with distance out from the center (left to right on the graphs). And oddly, even more jiggly at f/5.6!

Also pays to remember that shooting a 645-format lens on the S sensor (30x45mm crop instead of the full ~42x56mm film it was designed for) is basically shooting it as a half-frame lens.

But this may be the reason Zeiss and Kyocera pulled the plug on all the Contax lines, once digital began to move in - what they had planned to get away with on film was just no longer going to hold up when pixel-peeped from a double-digit-megapixel digital file. Either start all over from scratch - or give up.

Certainly makes one appreciate what Leica was able to do with the 45mm f/2.8 Elmarit-S (for a price!)

Scroll down a bit for one sample chart - or download Leica's entire technical data .pdf at the bottom of the page.

https://leica-camera.com/en-US/photography/lenses/s/elmarit-s-45mm-f2-8-asph

[jankap]

A test for decenter offers Jim Kasson on his blog.

[spiffariffic]

12 hours ago, adan said:

I certainly wouldn't discount the possibility this is simply an "ugly" version of the lens, as you describe.

Thanks for the background info and the link! I know it's not as performant as the Leica 45mm for pure sharpness. I really like the rendering though… except for this focal plane weirdness. (And obviously I like the price.)

But I don't think less-than-stellar MTF performance explains how I can have a zone of sharp focus at ~2ft, then out of focus rendering, and then a zone of sharp focus again at ~500ft, at f2.8! But correct me if I'm wrong.

The fuzziness on the ridge right in the 2nd image lines up with where the thick haze is, so that's definitely the ugly part.

I think the cropped nature of the sensor probably does hide the worst of this de-centered lens' flaws. If it were 25% of the price of a good one, instead of 50%, I'd probably keep it. It's very good up close.

 

Edited March 30, 2024 by spiffariffic