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Gbrad
Tinkerer
Username: Gbrad
Post Number: 3
Registered: 05-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 03, 2009 - 10:50 am: | 
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I was examining by Canon FTb in preparation for redoing light seals and noticed that that there is oil visible on the front of the iris blades of the Lens. Is this a concern that needs to be delta with? I've never noticed it before, but have never examined them closely before. |
Brianshaw
Tinkerer
Username: Brianshaw
Post Number: 59
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 03, 2009 - 11:02 am: |
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Yes, be concerned. The lens needs to be cleaned. The oil will slow down the aperture blades as they stop down and give bad exposure in some situations. Eventually they will simply stop closing down. |
Gbrad
Tinkerer
Username: Gbrad
Post Number: 4
Registered: 05-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 03, 2009 - 11:49 am: |
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I guess I better find a manual and read up on lens repair. Thanks for confirming my fears. |
Gez
Tinkerer
Username: Gez
Post Number: 92
Registered: 09-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 03, 2009 - 05:43 pm: |
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Is the lens in question an FD 50mm / 1.8? If it is, be aware that at least 3 different versions of this lens were manufactured. The last type though still having the chrome breech-lock ring is made mostly of reinforced plastic and is surprisingly easy to work on. |
Gbrad
Tinkerer
Username: Gbrad
Post Number: 5
Registered: 05-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, June 03, 2009 - 07:05 pm: |
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It is a 50mm / 1.4 SSC. I bought the camera in 1975 and it has taken good pictures over the years but, like me, it's showin it's age. Did some reading last night and think I can do this. My main hobby is overhauling/restoring old radios, have survived some real nightmares in those things. I will take pictures as I go and proceed slowly, then scream for help when that doesn't work. |
Gez
Tinkerer
Username: Gez
Post Number: 93
Registered: 09-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 04, 2009 - 03:52 am: |
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The FD 1.4 is a great lens and built in a solid traditional way. Rick Oleson has provided some good notes for this lens in a recent posting. The BL mount can be left on, and the whole aperture assembly comes out clean, there are no springs to disengage. Just flush clean as a unit, there is NO reason to disassemble the individual blades.
Now the important bit. With the front optical cell removed mount the lens on a body. Using the depth of field button stop the lens down to F16 and measure the diameter of the aperture hole. Fine nose calipers are best but drill bits are OK. Before unscrewing the 3 screws holding the aperture plate scribe their positions. This is critical as the screw holes on the aperture plate are slightly oversize and movement of the plate will effect the diameter of all aperture settings. It has been designed that way for fine adjustment!
On reassembly re-measure the diameter at F16, it should be about 2.07mm, the Canon service guide gives the upper and lower limits as 2.26mm and 1.89mm.
PS you will probably find oil inside the barrel too, just wipe it away with a cotton tip. If the internal glass surfaces are clean leave them alone, tiny bits of cotton dust only become apparent when assembly is complete! |
Charlie
Tinkerer
Username: Charlie
Post Number: 208
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 04, 2009 - 06:18 am: |
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I saw in Wikipedia that this is a match needle exposure system which I take to mean that you always manually set the aperture.If this is the case, I don't see why you need to clean the aperture blades. |
M_currie
Tinkerer
Username: M_currie
Post Number: 181
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 04, 2009 - 07:46 am: |
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Charlie: Manually set aperture or not, the lens is "automatic," in that you view and set aperture to the meter, both with the aperture fully open. Look at any relatively modern SLR as you set the aperture ring, and you'll see that the iris does not close. As in all such systems, the meter is reacting not to the change in light, but the change in aperture ring position. The iris itself doesn't close to the set aperture until you fire the shutter, whereupon a linkage operates it. It is here that the problem occurs, because it happens very quickly, and the blades must move very freely. |
Brianshaw
Tinkerer
Username: Brianshaw
Post Number: 60
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 04, 2009 - 10:44 am: |
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Wikipedia can be dangerous in the wrong hands! M-currie is absolutely correct. "relatively modern SLR" means any manufactured since about 1970. |
Gbrad
Tinkerer
Username: Gbrad
Post Number: 6
Registered: 05-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, June 04, 2009 - 10:16 pm: |
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Gez, Thanks for the info, I had already looked at a site by Rick Oleson. Removing the oil went real well, took time to get the diameter set, but think it's right on the money now. However, I need to go through the lens one more time and do a better job of getting the dust off the lenses. It's not real bad, but I want it as good as I can get it. |
Charlie
Tinkerer
Username: Charlie
Post Number: 209
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, June 05, 2009 - 05:56 am: |
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Hi M-currie, Thanks for the info (although I don't own any SLR, modern or otherwise). |
