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PLEASE zeiss tevidon help needed!
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PostPosted: Mon Jan 31, 2011 4:40 pm    Post subject: PLEASE zeiss tevidon help needed! Reply with quote
i have just received a zeiss tevidon 25/1.4 from a verydifficult seller. i put it on my ep2 via c mount>m4/3 adapter that works on all my other c mount lenses. the tevidon does not focus to infinity--in fact it works like a macro lens and will only focus very close up. the focus does change when i turn the focus ring, but really always remains blurry unless i am virtually on top of my subject. it seems to change focus when i stop down the aperture, but never enough to focus at infinity.

i have seen beautiful work with this lens on this forum at many different focal legnths including infinity, especially from klaus. can anyone tell me what is wrong with my copy????

i have had an ongoing dispute with this seller and it would help me tremendously if i could respond to him quickly...
thanks so much!
tony


PostPosted: Mon Jan 31, 2011 5:39 pm    Post subject: Reply with quote
If you turn the focus ring, does anything move inside the lens, some elements?
Is the lens complete? (Silly question, but you never know...)


PostPosted: Mon Jan 31, 2011 5:54 pm    Post subject: Reply with quote
hi carsten

no, nothing that i can hear or feel moves inside the lens at any time. and i am sorry to show my ignorance, but im not sure what yu mean by the lens beong complete--it seems as complete as any other lens i have, but i can check sonething specific if you suggest...

if it helps, i just set the focus at its closest point and moved toward an object until it was in perfect focus. i then stood still and moved the focus ring towards infinity and the object moved out of focus as it would be expected.

Last edited by rbelyell on Mon Jan 31, 2011 6:00 pm; edited 2 times in total


PostPosted: Mon Jan 31, 2011 5:56 pm    Post subject: Reply with quote
Zeiss Tevidon 25mm f1.4 require machine work to fit well into c-mount adapter. Need to cut from lens and adapter too.

Same case for longer Tevideons too.


PostPosted: Mon Jan 31, 2011 6:00 pm    Post subject: Reply with quote
hi attila

well, tbh, i have no problem fitting the lens into the adapter, it seems to screw on easily, stops with the aperture marker right in the middle, and seems perfectly tight--it doesnt move at all when focusing or changing aperture. i do have lenses of different varieties that dont seem to be a perfect fit with an adapter, like my mir 35mm and a couple of others, but really this one seems fine...


PostPosted: Mon Jan 31, 2011 6:08 pm    Post subject: Reply with quote
rbelyell wrote:
hi attila

well, tbh, i have no problem fitting the lens into the adapter, it seems to screw on easily, stops with the aperture marker right in the middle, and seems perfectly tight--it doesnt move at all when focusing or changing aperture. i do have lenses of different varieties that dont seem to be a perfect fit with an adapter, like my mir 35mm and a couple of others, but really this one seems fine...


Klaus can confirm it, all TEvideon 25mm f1.4 require machine works to work properly in c-mount adapter. I had this lens I sold it with note need to adjust it for c-mount. Currently I have Tevidon 75mm I did gave to my repair man to cut i'ts end to c-mount adapter.


PostPosted: Mon Jan 31, 2011 6:14 pm    Post subject: Reply with quote
can you please describe exactly what has to be done to the lens to get it to work properly? is the issue that the lens sits too far from the sensor, or are you saying the issue is the lens does not properly fit on the adapter? in my case the lens seems to FIT very well on the adapter, so i am confused....
thanks!


PostPosted: Mon Jan 31, 2011 6:19 pm    Post subject: Reply with quote
rbelyell wrote:
can you please describe exactly what has to be done to the lens to get it to work properly?


I don't know exactly on 25mm f1.4 , because I sold it without modification. Klaus know it , please ask him.
I had Zebra version of this lens.

on Tevidon 75mm need to cut from back of lens and from adapter too , at least this is what said my repair man in advance when I bought lens.


PostPosted: Mon Jan 31, 2011 7:04 pm    Post subject: Reply with quote
Yes, all Tevidons in c-mount need machining so as to match a certain c-mount adaptor [*].
Bring both to your machinist, he will make it fit. Don't be astonished if the infinity marks
does not exactly fit, this is a problem with most adaptors, some go beyond infinity, others
don't even reach it.

[*] this is well documented in many forums.


PostPosted: Mon Jan 31, 2011 8:45 pm    Post subject: Reply with quote
klaus thank you so much for your reply. unfortunately i still do not really understand what the problem is and i do not have a camera repair person that i can ask. can yiu, or anyone else help me understand:


1) is it a problem with the lens not fitting properly in the adapter. if this is the problem, i do not understand why my lens seems to fit the adapter perfectly. it screws in just like any other lens i have and sits very snug with no movement or vibration of any kind; or

2) is it a problem that without machining the lens sits on the adapter too far from the sensor and so cannot properly focus; or

3) is it some other problem?

i really appreciate your help because the seller is very nasty and unhelpful and i have to make a decison soon on whether to try to return or bring an action against him with ebay, OR depending on what i have to do, to try to fix it to work properly. that is why i am trying to understand this better.
thank you
tony


PostPosted: Mon Jan 31, 2011 10:55 pm    Post subject: Reply with quote
Found a pic of a modified Tevidon on flickr, this need to be done to ANY c-mount TEVIDON to fit some available c-mount adaptors.



A few millimters have to be machined off the mount for a correct infinity fit. Measure yourself: The c-mount innermost part has 37mm diamater usually, but the outside of a Tevidon c-mount has 40mm diameter. 40mm - 37mm = 3mm has be turned off on a lathe.


Or look at this ended auction Click here to see on Ebay that seller of c-mount adapters also explains it...

Hope you get it now...


PostPosted: Mon Jan 31, 2011 11:45 pm    Post subject: Reply with quote
klaus thank you for trying to explain it to me. i understand that you are saying the screw thread of the lens is too large for the adapter and so needs to be shaved. what i still do not understand is why my lens has no problem fitting into my adapter? as ive said a few times, my lens screws into my adapter just as easily as any other c mount lens i have. i have no problem screwing the lens into it. as a matter of fact, the aperture notch ends up perfectly centered at the top when the lens is fully screwed into the adapter. i do not have to force it, it seems to fit just perfectly.

given what you said, does my situation make any sense to you? is it normal that the lens seems to fit the adapter perfectly, yet in reality actually does not fit correctly?

thank you for your patience
tony


PostPosted: Tue Feb 01, 2011 12:36 am    Post subject: Reply with quote
rbelyell wrote:
klaus thank you for trying to explain it to me. i understand that you are saying the screw thread of the lens is too large for the adapter and so needs to be shaved. what i still do not understand is why my lens has no problem fitting into my adapter? as ive said a few times, my lens screws into my adapter just as easily as any other c mount lens i have. i have no problem screwing the lens into it. as a matter of fact, the aperture notch ends up perfectly centered at the top when the lens is fully screwed into the adapter. i do not have to force it, it seems to fit just perfectly.

given what you said, does my situation make any sense to you? is it normal that the lens seems to fit the adapter perfectly, yet in reality actually does not fit correctly?

thank you for your patience
tony


I think the problem is that although the lens screws into the adapter it doesn't screw all the way in and touch the inside of the adapter because the lens body comes into contact with the adapter a few turns before the base of the lens does


PostPosted: Tue Feb 01, 2011 12:45 am    Post subject: Reply with quote
oh i see, it appears to fit but in reality it is not able to screw in all the way unless the entire thread is shaved 3mm...ok, i got it.

so you dont bring this to a camera repair person, you bring it to a machinist? it seems it shouldnt cost too much to do...

thanks everyone!
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