| Author |
Message |
    
Ohm
Tinkerer
Username: Ohm
Post Number: 30
Registered: 09-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, June 18, 2010 - 09:08 am: | 
|
I have my Dad's old canon 100-200mm zoom lens and it has fungus on the inside of the front element, how hard would it be to disassemble the front of the lens and clean the glass, I think I saw one post detailing the disassemble process for FD lenses but I am not seeing it now. |
Tom_cheshire
Tinkerer
Username: Tom_cheshire
Post Number: 327
Registered: 04-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, June 18, 2010 - 10:36 am: |
|
If it is anything like the 135mm then you undo the ring and the glass drops out. Quick clean and put together again.
But the real question is "Why do Canon lenses get fungus on the backside of the front group so often?". It seems to be the location of choice for fungus in Canon. |
Gez
Tinkerer
Username: Gez
Post Number: 204
Registered: 09-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, June 18, 2010 - 12:39 pm: |
|
According to an old promotional leaflet with some cutaway diagrams of the old FD breech-lock lenses, the front retainer of this early zoom isn't a simple ring but is a substantial piece of metal holding a cemented doublet. If that is the case, it may not unscrew directly and there could be at least one grub screw hidden on the top part of the barrel.
Proceed with caution! |
Ohm
Tinkerer
Username: Ohm
Post Number: 31
Registered: 09-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, June 18, 2010 - 02:09 pm: |
|
The worst part is this lens has been cleaned twice already, when my Dad first got it, brand new back in the day  about 6 months after he bought it it got fungus. My Dad sent it in to get cleaned and they lost it!!! 6 Months later they found it again, cleaned it and returned it to him. A year or two later it got fungus again, he found a local place to cla it and it was fine for a few more years when it grew more and he said screw it. I just figured if I can get it apart relatively easily to clean it I will do so. I was noticing there are two slots in the top cap that go down lengthwise, between the lens shade and lens of course, so I think I might have to make a spanner to undo it as it doesn't seem to want to turn with fingers. |
Glenn
Tinkerer
Username: Glenn
Post Number: 784
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, June 19, 2010 - 08:15 am: |
|
There are three versions of this lens - two breech and the nFD version, all three have minor differences in construction. I can dig out the repair manuals if required, but from memory the front ring is the hood retainer - removal of this and the hood reveals the grub screws that hold the front section.
fungus in the longer Canon zooms of this period is not unusual, even after only six months. The internal zoom mechanism shifts a very large volume of air over the entire zoom range and this continual 'pumping' action can pull all manner of dirt and crud into the lens, the units being completely lacking in any form of sealing against ingress of dirt etc. To completely clean all traces of fungus spores from the lens, one must completely dismantle and 'disinfect' all interior surfaces - not just the glass surfaces. If this is not done you run the risk of leaving spores on the interior metal surfaces, which the internal air movements will soon deposit onto the internal glass surfaces. |
Ohm
Tinkerer
Username: Ohm
Post Number: 32
Registered: 09-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, June 19, 2010 - 08:54 pm: |
|
Cool thanks I will try to gently un-thread the front ring. |
Gyurmi
Tinkerer
Username: Gyurmi
Post Number: 16
Registered: 12-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, June 22, 2010 - 06:32 am: |
|
I had the FL version of this lens, which suffered from many ills including fungus. I took it completely apart and cleaned it, but did not think of 'disinfection'. What would you use for that? Would household mould killer work? (Unfortunately, most brands over here now double as bleach - I don't imagine it would be very helpful in this case, would it?) |
