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My lens can not focus far
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PostPosted: Mon Feb 26, 2018 10:03 pm    Post subject: My lens can not focus far Reply with quote
I bought a Carl Zeiss Sonnar 85mm f2.8 lens (Rollei mount) on Ebay.
Today I received it and the truth is that it is in good condition. So I was very happy doing the initial check ... everything seemed perfect, until I try to take a distant approach, surprise! I can not focus beyond 50 or 60 meters! There is the top of the focus ring marking infinite ... but the reality is that I can not focus far.
My camera is Olympus OM-D E-M1 in micro four thirds. I have many manual lenses, but this problem did not occur to me before.
Can anyone give me any clue as to what may be happening?
Should I return the lens to the seller?


Thanks for your attention.


PostPosted: Mon Feb 26, 2018 10:33 pm    Post subject: Reply with quote
If you have already another lens in QBM Rollei mount that focuses correctly at infinity on the same QBM to M43 adapter then the lens is obviously somehow defective. If not, your adapter may be too long as well.


PostPosted: Tue Feb 27, 2018 12:50 am    Post subject: Reply with quote
I agree with Thomas. Most likely issue is with adapter.


PostPosted: Tue Feb 27, 2018 7:45 am    Post subject: Reply with quote
Actually the adapter is correct. I have two lenses for the same Rollei-QBM mount, with them I can perfectly focus on any distant point.
Therefore, the problem is in the lens.
Now, the lens seems to be very good looking. What can happen that causes this problem?
I just checked the focus range. The minimum approach (1m) makes it right. Up to 2 approx. the approach corresponds to the scale of ring numbers, but from there the scale is not reliable. And now I can see that the maximum focus is much smaller than I thought ... it's around 20m. Can not focus beyond 20m!
I find it surprising.
I do not have an explanation to this mystery. Maybe someone disassembly this lens and then it did not assemble correctly?


PostPosted: Tue Feb 27, 2018 9:11 am    Post subject: Reply with quote
Lepersson wrote:
Actually the adapter is correct. I have two lenses for the same Rollei-QBM mount, with them I can perfectly focus on any distant point.
Therefore, the problem is in the lens.
Now, the lens seems to be very good looking. What can happen that causes this problem?
...
Can not focus beyond 20m!
I find it surprising.
I do not have an explanation to this mystery. Maybe someone disassembly this lens and then it did not assemble correctly?

I remember the times when Minolta (AF) acifionados were keenly waiting for a real DSLR, back in 2000-2003. Minolta then said the tolerances of their (AF) lenses were too large to use them on digital sensors. In fact, when finally the Dynax 7D came out i had to re-calibrate several of my Minolta AF lenses to allow for infinity focusing.

I would guess that your lens has a similar problem - either from manufacturing or from a later disassembling/reassembling.
The same problem occurs with quite a few of my vintage lenses. Therefore (especially for lens testing) i usually own two different adapters for each mount:

1) One which is a bit "shorter" than it actually should be (and thus allows focusing beyond infinity) => used for testing ordinary prime lenses (EDIT: the "prost" adapters are my preferred "short ones")
2) and another one which seems to have the "accurate" length => used for testing zooms where the correct distance betwen master lens and sensor ist important

Stephan


PostPosted: Tue Feb 27, 2018 9:17 am    Post subject: Reply with quote
When you try to focus toward infinity does it fell like the focus ring hits the stop screw or that something in the rear part of the lens barrel hits the mount mechanics? Does the aperture work properly with the lens at infinity mark respectively at closest focus distance?
If someone relubed the lens and missed the helicoid alignment, the aperture control tab either will hit the inner of the lens mount (at infinity) or escape the metal guide at close focus distance. The mechanical tolerances in this lens are very tight.


PostPosted: Tue Feb 27, 2018 9:52 am    Post subject: Reply with quote
Lepersson wrote:
Actually the adapter is correct. I have two lenses for the same Rollei-QBM mount, with them I can perfectly focus on any distant point.
Therefore, the problem is in the lens.


Your reasoning doesn't necessarily hold true. Longer focal lengths are more tolerant of poor adapters, as the change in registration has less effect on their focus (and they often have focus travel that goes beyond infinity too). However the problem lens you have is 85mm so isn't one of the lenses most prone to issues. If your other lenses are shorter than 85mm then it does suggest your adapter is OK.

I've recently shimmed a MFT-MD adapter to bring it closer to the internets difference in registration. When testing it with a cheap 28-210 zoom I found the focus is a touch short of infinity at the 210mm end of the zoom while infinity focus is reached quite a long way before the set mark at the 28mm end of the zoom. My adapter can't be the fault on that Smile


PostPosted: Tue Feb 27, 2018 10:03 am    Post subject: Reply with quote
lucca1x wrote:
When you try to focus toward infinity does it fell like the focus ring hits the stop screw or that something in the rear part of the lens barrel hits the mount mechanics? Does the aperture work properly with the lens at infinity mark respectively at closest focus distance?


No problem of those happens.

DConvert wrote:
If your other lenses are shorter than 85mm then it does suggest your adapter is OK.


Rollei 35mm and Voigtländer 35mm
Therefore shorter.


PostPosted: Tue Feb 27, 2018 10:35 am    Post subject: Reply with quote
Lepersson wrote:
lucca1x wrote:
When you try to focus toward infinity does it fell like the focus ring hits the stop screw or that something in the rear part of the lens barrel hits the mount mechanics? Does the aperture work properly with the lens at infinity mark respectively at closest focus distance?


No problem of those happens.

DConvert wrote:
If your other lenses are shorter than 85mm then it does suggest your adapter is OK.


Rollei 35mm and Voigtländer 35mm
Therefore shorter.


In this case I'll go with the adapter being a bit long. Afaik the dof is smaller on longer lenses that's why the 35mm lenses could be ok on the same adaptor and the 85mm not. I would try to test another adapter, eventually if you know someone who owns a Rolleiflex sl35 ask him/her to allow you to mount the lenses and check the infinity in viewfinder.
This is my opinion if the lens behaves mechanically correct (lens barrel not hitting the mount and the aperture working at any focus distance). I'm sure other members here will also try to help.


PostPosted: Tue Feb 27, 2018 10:40 am    Post subject: Reply with quote
I begin to believe that someone did an incorrect assembly. But if someone disassembled this lens he was very careful because I can not see traces.

Anyway, I found this video of someone correcting infinite focus on a Rollei. Apparently it's easy, although you need patience.

https://youtu.be/bFA4VFMEicM

Although my CZ sonar 85 doesn't have that "construction", someone comments after the video that he managed to adjust his Sonnar 2.8 85 in the same way!!

This gives me hope ... today I will "twist" the nose of my sonnar and I will tell you if I later discovered three screws in front of me ... or else I had a CZ destroyed in front of me. Shocked


PostPosted: Tue Feb 27, 2018 11:33 am    Post subject: Reply with quote
The workaround shown in that video also works on the full metal lens body version.
Just don't unscrew the lens block all the way out. It will be difficult to put it back in the correct position if you don't mark the exit point.
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