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Mike Kovacs
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, August 02, 2005 - 07:07 pm: | 
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Has anyone ever tried repolishing a lens with lots of fine cleaning marks?
I have a prewar CZJ Sonnar 50/2 collapsible that is afflicted with these on the front element. The lens is uncoated. |
Jani Heikkinen
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, August 02, 2005 - 09:10 pm: |
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I have usually sent any lenses in need of polishing to a local optician who makes lenses for observatories etc. and he does a wonderful work with old lenses. The only problem is that the scratches cannot be too deep, otherwise they cannot be removed. So I recommend using a professional for the job. |
mike kovacs
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, August 03, 2005 - 07:00 am: |
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I emailed John at Focal Point but I know it probably won't be cheap. The idea to use an optician is a good one that I will have to explore.
The lens has a web of very fine scratches like you might get from careless cleaning. |
Jani Heikkinen
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, August 03, 2005 - 11:48 pm: |
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Hi Mike!
I am not sure if the optician is the correct word for describing the work that he does, but in general he designs, makes and repairs lenses and mirrors for optical systems. As he did the polishing inbetween his other work, it cost me for example only between 20-30 euros for one tessar rear element with 2 scratched surfaces. So I suggest you find some company that makes optics and ask from them. |
Winfried
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, August 04, 2005 - 12:17 am: |
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In Germany there is a difference between 'precision opticians' (Feinoptiker) and 'ophtalmologic opticians' (Augenoptiker). A 'Feinoptiker' actually deals with manual and automatic manufacturing of optical components (from bare blocks of optical glass to ready-to-use lenses), and (re-)polishing surfaces is part of their work. Remember that all lenses were manufactured mostly on manual equipment until several decades ago.
The normal optician down the road who takes care of your eyeglasses probably has never learned how to do all this, and even if he had the equipment he would not be able to handle it.
I once stumbled across the website of a german precision optician who offers repair services for all kinds of optical equipment, including repolishing telescope mirrors etc. |
Ezio
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, August 04, 2005 - 12:40 am: |
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I understand that this is practical option only for uncoated lenses (as in Mike's case) because repolishing will necessarily remove the coating. Can anyone confirm this? |
Winfried
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, August 04, 2005 - 02:56 am: |
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Yes, of course re-polishing (the polishing process during original manufacturing removes 1 my-m - 1/1000mm - of thickness or more) will remove the coating. Coating thickness is much less than 1 my-m.
However, it is not impossible to have lens elements re-coated. Cemented lens groups have to be separated prior to this process (and, of course, re-cemented). |
Mike Kovacs
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, August 04, 2005 - 08:40 am: |
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Maybe I should talk to someone in our Physics and Astronomy department? I bet they must need this type of work done from time to time. |
Stuart Willis
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 06, 2005 - 07:27 am: |
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Mike ... your last message suggests to me that you have a University connection. There are optical laboratories which specialise in the repolishing of lenses for cameras and microscopes - and the production of all manner of prisms.
Your Uni (or hospital ??) would certainly be able to direct you.
In Australia we have at least one world-class such lab - but we do not have a lab which can re-hard-coat with magnesium fluoride. Soft coating is OK but one has thereafter to be very very gentle with any cleaning process. Since the answer is to "keep it clean and not keep cleaning it" just attach a Skylight or UV filter fom day one. My soft-coated Rolleiflex 3.5 Xenotar was assigned such a filter after the process and 8 years later it is still immaculate.
Hope this helps - a bit !
Stuart Willis |
