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Minolta 100 mm 2.5 MD III fungus cleaning
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PostPosted: Tue Jul 23, 2024 12:54 pm    Post subject: Minolta 100 mm 2.5 MD III fungus cleaning Reply with quote

Hello, everyone. I purchased a lot in eBay that includes three Minolta lenses affected by fungus. The 50 1.7 is of little interest to me, and I am leaving it for last. The 24 2.8 unfortunately recatracts internal traces of a botched cleaning, but still works well (although it doesn't blow me away from the first results--CA and softness on edges); what I would like to do is clean the 100 2.5 MDIII. I have already eliminated trace of the fungus between the two main lens groups, and the lens already provides outstanding results, but I would like to clean the front group elements as well, which unfortunately in the latest Minolta lenses are encased through the rebating of the aluminum cylinder in which they are housed. Having a lathe (three actually) at my disposal, I would have thought to eat the rebated edge, take out the elements, and after cleaning reposition them and glue them (under pressure) with two-component glue along the edge. I have good manual dexterity, and the operation is likely within my reach, but I ask if anyone has a better idea.

Thank you all and have a good time


PostPosted: Tue Jul 23, 2024 1:40 pm    Post subject: Reply with quote

On-line information will be easier to find if you search for the correct terminology: these are not called rebated lens mounts, but burnished lens mounts.

I have only had to deal with this once in a Minolta lens; but on that lens (MDIII 50/1.7 from memory) that burnished lip was just plastic so I could shave it off with a very sharp hobby knife (taking care of the fingers!!).

The lenses were a tight fit so they stayed in place by themselves after pressing them back in, but to be sure I used a small amount of modelling glue (MEK) around the perimeter which which has worked so far...

Some relevant web info:

https://www.largeformatphotography.info/forum/showthread.php?64500-Burnished-lens-mounting

https://www.cloudynights.com/topic/756083-lens-removal-from-burnished-mount/

Page 18 in the following pdf (most of the images in this pdf have been taken from Yoder "Mounting Optics in Optical Instruments, an excellent book for details like this):
https://wp.optics.arizona.edu/optomech/wp-content/uploads/sites/53/2016/08/26-Mounting-of-lenses-1.pdf


PostPosted: Tue Jul 23, 2024 3:29 pm    Post subject: Reply with quote

RokkorDoctor wrote:
On-line information will be easier to find if you search for the correct terminology: these are not called rebated lens mounts, but burnished lens mounts.

I have only had to deal with this once in a Minolta lens; but on that lens (MDIII 50/1.7 from memory) that burnished lip was just plastic so I could shave it off with a very sharp hobby knife (taking care of the fingers!!).

The lenses were a tight fit so they stayed in place by themselves after pressing them back in, but to be sure I used a small amount of modelling glue (MEK) around the perimeter which which has worked so far...

Some relevant web info:

https://www.largeformatphotography.info/forum/showthread.php?64500-Burnished-lens-mounting

https://www.cloudynights.com/topic/756083-lens-removal-from-burnished-mount/

Page 18 in the following pdf (most of the images in this pdf have been taken from Yoder "Mounting Optics in Optical Instruments, an excellent book for details like this):
https://wp.optics.arizona.edu/optomech/wp-content/uploads/sites/53/2016/08/26-Mounting-of-lenses-1.pdf


Thank you very much, very helpful!


PostPosted: Tue Jul 23, 2024 5:12 pm    Post subject: Reply with quote

i have same issue with the md 35-70mm macro, but i´m not sure i would take it apart (yet), wonder how many other minolta´s suffer from this less smart option (not cheap to service)


PostPosted: Tue Jul 23, 2024 5:17 pm    Post subject: Reply with quote

kiddo wrote:
i have same issue with the md 35-70mm macro, but i´m not sure i would take it apart (yet), wonder how many other minolta´s suffer from this less smart option (not cheap to service)


The 45/2 for sure