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Archive 2011 · Zeiss, Infinite focus play, their response

  
 
cputeq
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p.1 #1 · p.1 #1 · Zeiss, Infinite focus play, their response


To settle any question about Zeiss infinity focus play, at least for their 35/2, here's the response. I decided to make a new thread in case someone does a search in the future.

First, my quesiton to Zeiss on my 35/2 infinity "slop":


I just received my Zeiss 35mm f/2 lens in Canon EOS mount. I have it attached to a 5D mark II camera. Everything works wonderfully except infinity focus.

Although the distance marker stops at the infinity symbol, it appears long-range focus moves PAST infinity - I must back off the lens about 1-2 mm to achieve sharp focus at infinite targets, and I have verified this using 10x magnified live view.

Is this normal?



The response:


Dear Customer,

Thank you for your inquiry to Carl Zeiss.

Some play in the focus ring at infinity and beyond is possible. This avoid problems with the infinity adjustment when tolerances of the flange focal distance of the camera body are to high. 1mm sounds ok 2mm is probably to much. But when you don`t have an application where you need a reliable stop at infinity (eg aerial photography) this doesn`t matter at all. If you like to have an alternate adjustment we would need camera and lens to do this kind of service. Then we could change the flange focal distance in
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Apr 27, 2011 at 02:36 PM
AhamB
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p.1 #2 · p.1 #2 · Zeiss, Infinite focus play, their response


Thanks for this. So it's what I thought, they focus beyond infinity in order to accomodate for tolerances in the FFD.


Apr 27, 2011 at 03:22 PM
jotdeh
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p.1 #3 · p.1 #3 · Zeiss, Infinite focus play, their response


Yeah, play it safe. People will generally be more upset about not achieving infinity focus than they would be about possibly focusing "beyond" infinity.


Apr 27, 2011 at 03:51 PM
mMontag
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p.1 #4 · p.1 #4 · Zeiss, Infinite focus play, their response


I have a few auto-zooms that can reach (manually) beyond infinity - it's been stated this is to allow for thermal expansion in regard to the moving cam components.

Just curious - what scene(s) would require a true infinity setting - astronomy, aerial and far distant telephoto subjects - typically focus for most scenes will be a variation of a hyper-focal setting - 2mm is a lot - beyond infinity everything is out of focus.

Is the infinity adjustment on the ZE's under the faceplate? Has anyone tried adjusting one?



Apr 27, 2011 at 04:35 PM
wayne seltzer
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p.1 #5 · p.1 #5 · Zeiss, Infinite focus play, their response


My ZF 35/2, ZE 21/2.8, and ZE 50MP all reach infinity at the infinity stop on my 1ds3. I think there are tighter tolerances on the 1ds bodies than the 5d's.


Apr 27, 2011 at 05:38 PM
atran
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p.1 #6 · p.1 #6 · Zeiss, Infinite focus play, their response


Great to hear that you get a response cputeq. Do you plan to go forward with the adjustment and send it your equipment?


Apr 27, 2011 at 06:06 PM
mMontag
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p.1 #7 · p.1 #7 · Zeiss, Infinite focus play, their response


All of my Contax primes are at an infinity stop on a 5D - or very, very close - being used lenses it's hard to know if they were factory set or adjusted by their former owners.


Apr 27, 2011 at 07:05 PM
cputeq
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p.1 #8 · p.1 #8 · Zeiss, Infinite focus play, their response


atran wrote:
Great to hear that you get a response cputeq. Do you plan to go forward with the adjustment and send it your equipment?


No, I just needed to know if I had a faulty lens or not. I typically don't shoot infinity in fast-moving situations, but instead in instances of landscape, etc. where I'm going to take my time anyway.

Most of the time I'm taking advantage of the bokeh, etc. of the lens and shooting at closer distances.

So, while I'm a bit bummed at not having a fast way to get exact infinity, i've almost memorized it enough to where I could probably pull it off if I really needed to, but it's not bugging me enough to send in my camera and lens for adjustment (that would cost who-knows-what).




Apr 27, 2011 at 07:29 PM
edwardkaraa
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p.1 #9 · p.1 #9 · Zeiss, Infinite focus play, their response


mMontag wrote:
All of my Contax primes are at an infinity stop on a 5D - or very, very close - being used lenses it's hard to know if they were factory set or adjusted by their former owners.


I suspect that Contax lenses were built to tighter tolerances than the current ones made by cosina. Even the mechanical characteristics seem better on the Contax. It's all a matter of pricing I guess.



Apr 27, 2011 at 10:24 PM
denoir
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p.1 #10 · p.1 #10 · Zeiss, Infinite focus play, their response


wayne seltzer wrote:
My ZF 35/2, ZE 21/2.8, and ZE 50MP all reach infinity at the infinity stop on my 1ds3. I think there are tighter tolerances on the 1ds bodies than the 5d's.


The 1Ds bodies should have tighter tolerances, but in this case it would seem that you weren't lucky. If as Zeiss say they leave a mm of buffer in the focus then on a perfectly aligned sensor with the expected FFD it should be a mm off, and not dead on.

This brings me to a more general question - how could one ever know that the mechanical stop is at optical infinity and not front focusing slightly? If it is slightly off the effect would be a small degradation in sharpness. I don't see how you could detect it though unless it is really severe.



Apr 27, 2011 at 11:01 PM
edwardkaraa
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p.1 #11 · p.1 #11 · Zeiss, Infinite focus play, their response


I think this can be seen by shooting a landscape on a clear day WO.


Apr 27, 2011 at 11:35 PM
sebboh
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p.1 #12 · p.1 #12 · Zeiss, Infinite focus play, their response


mMontag wrote:
I have a few auto-zooms that can reach (manually) beyond infinity - it's been stated this is to allow for thermal expansion in regard to the moving cam components.


i've only heard of this applied to telephoto lenses where there is also the added benefit of greater manual focusing ease at distances near infinity. all such lenses that i've used allow you to focus past infinity on the focus scale so that you are aware the hard stop is not infinity. i'm surprised zeiss doesn't do this if they are purposely allowing focus a bit past infinity.



Apr 28, 2011 at 12:17 AM





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