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Dsides
Tinkerer
Username: Dsides
Post Number: 6
Registered: 04-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 01, 2009 - 08:18 am: | 
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I noticed the other day that my 35mm lens (my favorite!) will no longer focus to infinity. I put it on my wifes camera, and had the same problem. I haven't dropped it or anything, and just used it with great results about a month ago. Are these lenses adjustable, or does it involve taking it completely apart? |
Glenn
Tinkerer
Username: Glenn
Post Number: 563
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 01, 2009 - 10:27 am: |
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Yes, all Canon FD lenses are fully adjustable; however, to give you the proper answer more details are needed.
1/ Is the lens a breech mount or nFD model?
2/By 'no longer focus to infinity', what do you actually mean?
a/You cannot physically turn the focus ring so that infinity aligns with the focus datum?
b/Focus ring and datum align at infinity but distant objects do not appear in focus on the screen?
c/Actual negatives show out of focus objects at infinity?
The problem is if infinity focus has gone AWOL, there is no mode of failure that can occur to the actual helical whilst the lens rests in the camera bag - not that I know of anyway. Are you positive that nothing 'nasty' occurred after your 'great results' - a ham fisted friend perhaps?
A failure that can suddenly appear is a stuck diaphragm. Because of their inherent greater depth of field at maximum aperture, wide angle lenses lenses do not always give a 'snappy' indication on the screen, that the image is in focus. If the diaphragm is stuck partially stopped down, the lens will appear even more difficult to focus on the screen.
If you can narrow down the unknowns, it will be possible to give a more direct route to the solution of your problem. |
Dsides
Tinkerer
Username: Dsides
Post Number: 7
Registered: 04-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 01, 2009 - 11:48 am: |
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It is a breech mount model (the radioactive one).
When I focus on something more than about 120 yards away (tree, street light, flag pole) the image in the split screen doesn't come together.
The ring turns freely to the infinity mark.
Haven't run a roll through it yet. Someone suggested it might be the focus screen on my camera (T70), so I checked it on my wifes AE-1 and it still didn't focus. Works great from six inches on up...
Here's a shot from the last roll I used it on.
http://www.flickr.com/photos/dcsides/3442001861/ |
Glenn
Tinkerer
Username: Glenn
Post Number: 565
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, May 01, 2009 - 06:46 pm: |
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I will have to dig out my breech manuals, problem is I do not think I have the specific data for your lens.
I presume you are saying the split screen worked properly, when you took the linked photograph.
If you actually mean what you say in the last sentence of forth paragraph - the lens now focuses down to six inches - it would appear that the optical assembly has somehow become partially unscrewed out of the helical assembly. There is no way that this lens will focus down to such a short distance in normal circumstances, unless close-up lenses or extension tubes/bellows are used. Will you confirm the six inch min focus please.
With the lens mounted on the body - is there any excessive radial movement, when you hold the body and try and gently rotate the front of the lens? Try this with the focus ring at min, mid and max focus distances.
I do not know the construction of this lens off hand, I will have to find the manual before I can state what may have come loose. Will dig it out this weekend. |
Dsides
Tinkerer
Username: Dsides
Post Number: 9
Registered: 04-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 05, 2009 - 09:10 am: |
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Sorry about the late response, I work weekends. I didn't notice any problem when the attached photograph was taken. No one other than myself has touched my equipment - although I'm sure I could have knocked it against something at some point (cringe). Seems like I would have noticed, but I see no way for the lens to suddenly "decide" to have a problem with no cause.
The lens will focus at 7.5 inches from the front of the lens (11.25 inches from the "film plane"). It appears to focus at exactly 10 feet when the focus ring is at the "10 ft" mark.
There is minimal play (no more than would be expected from a 34 year old lens) or movement when attached to the camera body. |
Glenn
Tinkerer
Username: Glenn
Post Number: 570
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 05, 2009 - 11:05 am: |
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Your second paragraph has me very puzzled!! The minimum focus distance of all the breech 35/f2 lenses is specified as 0.3 metres, which is as near as damn 11.75 inches - so your lens appears to focus reasonably OK, allowing for measurement errors etc. I had assumed your previous quote of 'six inches' was measured from the film plane.
There is obviously nothing wrong with the focusing mechanism - you can check this by using the ground glass part of the screen when focusing on an object at infinity.
As I previously stated - it is difficult to get a 'clear' split image when one tries to focus with a lens stopped down. I still think your problem stems from, 1/ lens was manually stopped down when you tried to focus. 2/ The iris mechanism is 'sticking' some times and not fully opening after an exposure. Look into the front of the lens and observe the aperture blades moving, when you fire the shutter a few times. The iris should open to max after every 'exposure', you will soon see if it 'hangs' in a stopped down position. Do not only do this test on minimum aperture, the return spring may overcome any 'stickiness if it is fully stretched. Work down from maximum aperture and observe what happens in the mid aperture values.
I will await your observations with interest! |
Dsides
Tinkerer
Username: Dsides
Post Number: 10
Registered: 04-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 05, 2009 - 01:11 pm: |
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I focus with the lens wide open, as the T70 isn't capable of stopping down manually. The iris operates smoothly on each stop from 2 - 16.
Your second paragraph is where I'm finding the problem - the distant objects never finish "lining up" at the split when I get to the infinity mark (when the focus ring of the lens stops turning).
It's a mystery... I'll just shoot everything over 100 yards away on f16 and hope the DOF takes care of it. |
Glenn
Tinkerer
Username: Glenn
Post Number: 571
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 05, 2009 - 03:23 pm: |
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David,
Not that I doubt you, but just to recap. The problem with the 'split' just suddenly appeared after a long period of apparent normal use, is this correct? If the lens was mine I would take some test negs of a building side, bill board or other flat object with clearly defined features. Use max aperture and make sure you can move a long way from the subject.
If I actually had this lens in my hands the problem would probably be simple to solve: however, doing it all over the net is possibly making a mountain out of a mole hill. |
Dsides
Tinkerer
Username: Dsides
Post Number: 11
Registered: 04-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, May 05, 2009 - 05:40 pm: |
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That is correct (and why I found it so strange). I'll run a roll through it and see what shows up on film.
Thanks for wrinkling your brow for me! |
