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Cooltouch
Tinkerer
Username: Cooltouch
Post Number: 87
Registered: 01-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, April 21, 2011 - 05:02 pm: | 
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I just bought this lens and I'm having quite a bit of fun with it so far. I got a good deal on it because it has a few very small stars of fungus beginning to form. Of course, I would like it to be perfect, so I want to get rid of the fungus, especially since I don't want it to get any worse.
I just found out today that because this is an IF lens, this area of the lens can be very touchy to get back right during reassembly. And this is the area I need to get to because this is where the fungus is.
Normally when I work on a lens, I just tear into it and learn as I go. So far, I've been able to figure out how to get them back together again so they operate properly. But I sure would hate it if I ran into a really sticky problem with this one and wound up with a pile of dismantled components that I'll have to take to a repair guy in a box.
So, I'm wondering if anyone here has dismantled an IF Canon lens before and if it is indeed as tricky to maintain proper focus with this assembly as I've been told. |
Glenn
Tinkerer
Username: Glenn
Post Number: 912
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 22, 2011 - 10:01 am: |
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Very easy to take apart and equally easy to reassemble; however, you will then have a useless piece of junk!! Unfortunately I do not have the full Canon adjustment notes for your lens, but the ones for the 300mm IF talk about a focus tolerance of 0.02mm, a focusing scale index tolerance of one line and having to check the resolution by the projection method. The resolution table gives axial and zonal resolution in line pairs per mm out to 20mm off axis.
The official repair notes suffer from the usual Canon problem, they assume one has attended their technician's course.
If you email me your address I will photocopy the 300mm notes on focus adjustment etc and the assembly breakdown after the hols - I am sure the internal assemblies are the same, just different dimensions. So you should gain some knowledge useful for the 400mm. The documents will not scan successfully. |
Cooltouch
Tinkerer
Username: Cooltouch
Post Number: 88
Registered: 01-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 22, 2011 - 11:23 am: |
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Thanks for the response, Glenn. Given your description of tolerances, etc., it sounds more like to me I might ought not mess with things. If it were your lens, would you try dismantling it? |
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