Contax Zeiss > Leitax > Metabones EF-MFT > Bmpcc4k

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Circle of Confusion

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Contax Zeiss > Leitax > Metabones EF-MFT > Bmpcc4k

PostSat Jan 18, 2020 7:02 pm

I’m hoping to find answers from those who have experience with this kind of setup but other contribution is welcome too...

So, the title tells you what I’m dealing with. The problem is focus to infinity. I need to stop down to f5.6 or even f8 with the 28mm f2 to have infinity in focus. With my 50mm f1.7 I need to stop down to f4 to be in focus.

Is this normal? Shouldn’t infinity be in focus no matter what the aperture is?

Shouldn’t everything beyond the infinity distance be in focus? No matter if it’s 20m or 100m away.

Sure, this is old glass etc. but could there be a problem with the overall setup?

Thanks for your help!
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zakforsman

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Re: Contax Zeiss > Leitax > Metabones EF-MFT > Bmpcc4k

PostSat Jan 18, 2020 7:11 pm

I use Contax-Zeiss lenses with EF Leitax adapters. While I haven't used them on a Pocket 4K, I have used them with a M43-EF Metabones XL (.64x) on a GH5s and Z-Cam E2, and the only lens I couldn't reach infinity on was a 25mm f2.8. All the other lenses (18/4.0, 28/2.0, 35/1.4, 50/1.4, 85/1.4, 135/2.0) could reach infinity wide open.

The issue you're having is likely with the Metabones. I was able to get my 25mm to reach infinity by adjusting the rear optical element in the speedbooster. There are plenty of tutorials for that out there.
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Circle of Confusion

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Re: Contax Zeiss > Leitax > Metabones EF-MFT > Bmpcc4k

PostSat Jan 18, 2020 7:28 pm

Hey Zak, thanks for your reply.

I forgot to mention, I tested the 28mm f2 today with a Canon dslr today and infinity was sharp....

That tells me there is something fishy with with the Contax/Metabones combo. But I lack the expertise to say what it is.

But calibrating Metabones every time I change the lens is not the real world answer, way too impractical!

A little help, anyone?!
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Uli Plank

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Re: Contax Zeiss > Leitax > Metabones EF-MFT > Bmpcc4k

PostSat Jan 18, 2020 8:56 pm

Once the Metabones is calibrated, it should work with all lenses that are not out of alignment themselves.
I use a Metabones Contax to E-mount with several Zeiss lenses. BTW, wides are more critical.
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John Griffin

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Re: Contax Zeiss > Leitax > Metabones EF-MFT > Bmpcc4k

PostSat Jan 18, 2020 10:11 pm

You are stacking 2 adaptors with old glass so it would be more of a surprise if you did hit infinity focus at the lens infinity hard stop. Adjusting the metabones so all lenses overshoot infinity is the easiest solution. If you want all your lenses to hit infinity at the hard stop on the focus ring you will have to partially dismantle each lens and adjust the infinity calibration. YouTube will be full of how-to videos for this.
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Howard Roll

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Re: Contax Zeiss > Leitax > Metabones EF-MFT > Bmpcc4k

PostSun Jan 19, 2020 3:29 am

Circle of Confusion wrote:Hey Zak, thanks for your reply.

I forgot to mention, I tested the 28mm f2 today with a Canon dslr today and infinity was sharp....

That tells me there is something fishy with with the Contax/Metabones combo. But I lack the expertise to say what it is.

But calibrating Metabones every time I change the lens is not the real world answer, way too impractical!

A little help, anyone?!


I wouldn't touch your lenses, it's obviously a problem with the speedbooster. The fact that you can get infinity when you stop down means it's not that far out. The math tracks as well, if the 28mm was sharp at F8, and the 50mm was sharp at f4, a 100mm should be sharp at f2.0.

Good Luck
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Denis Kazlowski

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Re: Contax Zeiss > Leitax > Metabones EF-MFT > Bmpcc4k

PostSun Jan 19, 2020 7:49 am

Circle of Confusion wrote:I’m hoping to find answers from those who have experience with this kind of setup but other contribution is welcome too...

So, the title tells you what I’m dealing with. The problem is focus to infinity. I need to stop down to f5.6 or even f8 with the 28mm f2 to have infinity in focus. With my 50mm f1.7 I need to stop down to f4 to be in focus.

Is this normal? Shouldn’t infinity be in focus no matter what the aperture is?

Shouldn’t everything beyond the infinity distance be in focus? No matter if it’s 20m or 100m away.

Sure, this is old glass etc. but could there be a problem with the overall setup?

Thanks for your help!


Your problem is the Contax part of that lens equation vs Contax 35mm... which are indeed different. Good glass but only for the right platform. Your FFD is off, thusly no infinity.
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Uli Plank

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Re: Contax Zeiss > Leitax > Metabones EF-MFT > Bmpcc4k

PostSun Jan 19, 2020 2:01 pm

It's absolutely normal that all photographic lenses go a tad beyond infinity, this is meant to account for extreme temperatures.

But if you can adjust the Metabones to be fine for the 28mm, all longer lenses should work too if not severely out of alignment.
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John Griffin

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Re: Contax Zeiss > Leitax > Metabones EF-MFT > Bmpcc4k

PostSun Jan 19, 2020 2:54 pm

Uli Plank wrote:It's absolutely normal that all photographic lenses go a tad beyond infinity, this is meant to account for extreme temperatures.


Only large complex lenses have this facility as thermal expansion of the lens barrel can be significant enough. Small manual focus primes (especially legacy ones from SLR film days) should hit infinity and not go past it. Just to put things in perspective if a 28mm lens is mounted only 0.03mm further away from the sensor ( due to a badly made or badly fitting adapter) then you won't be able to focus further than 25m. Mostly adapter manufacturers make their adapters thinner to avoid this but then this creates other issues with lenses that have internal floating element focusing systems.
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Howard Roll

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Re: Contax Zeiss > Leitax > Metabones EF-MFT > Bmpcc4k

PostSun Jan 19, 2020 5:51 pm

Here’s the Metabones link that explains the process of setting the back focus of the cell.

https://www.metabones.com/article/of/in ... oster-only

Good Luck
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Circle of Confusion

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Re: Contax Zeiss > Leitax > Metabones EF-MFT > Bmpcc4k

PostSun Jan 19, 2020 8:53 pm

Just to be clear, it wasn't going beyond infinity. It didn't reach infinity.

But anyway, I actually did a test adjusting the speedbooster and got it to "focus" but the image quality was not acceptable. It was still blurry and distorted in a weird way. Also, all the other lenses lost their infinity focus so it was not a practical solution.

I'm convinced that particular lens needs a major overhaul and I will not be buying it for the asking price. Too bad... The "Hollywood" would have been a nice addition.

Thanks for your help, everyone!
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zakforsman

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Re: Contax Zeiss > Leitax > Metabones EF-MFT > Bmpcc4k

PostTue Jan 21, 2020 1:51 am

You have to make sure the rear element isn't off-kilter. That's prbably why you're seeing some strange blurriness in the image. After adjusting it, make sure that it's also seated perfectly parallel. I used to use gravity to do this by laying it face down before tightening it up.

Speedboosters work well with modern lenses, but with vintage glass, it amplifies their weaknesses. The minor chromatic aberration in Contaz Zeiss lenses is made worse. A lot worse. After trying everything i could, the only way to get my Leitax adapted vintage lenses (Contax Zeiss & Leica-R) looking their best, was to ditch the speedbooster completely. I now use them on cameras with full frame sensors. They have never looked better than they have paired with my Panasonic S1H and Z-Cam F6.

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