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Ben
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 16, 2006 - 02:33 pm: | 
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I finally got around to working on my spare junky 50mm 1.8(breech lock). I was following Rick Oleson's excellent directions for the 1.4 which matched up very well, until I got to the diaphragm. According to him, once the three screws are removed, the diaphragm should lift out as an assembly. When I attempted this, the whole thing came apart, and I can't quite see how to get it back together.
As it is now, I have the top plate, five blades(which I hope is all of them). Inside of the lens, there is a silver ring attached to a spring simply laying in there. I can see the other end of the stopdown lever that appears to interact with the little silver ring, but I can't quite figure out how.
Can anyone either provide a description of reassembly or some sort of pictures? Thanks.
By the way, there is some fugus on what I guess is the inside of the front element. I'm guessing that I'd probably have to disassemble the front group to get at this. Is it worth it to attempt this? It's located close to the edge, so it probably won't matter unless I have the lens wide open, but I wouldn't mind to remove this.
And, I know that I can replace the lens very cheaply. I have another one that cost me all of $1.25 off of Ebay and is in excellent shape-I wanted to see if I could end up with two decent working 50mm lenses. If I end up completely destroying this one, it's no big loss.
Thanks,
Ben |
Glenn Middleton
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 16, 2006 - 06:32 pm: |
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If you had removed the correct three screws, then you would have had no problems. Even if you reassemble the diaphragm, the lens will not function correctly unless you calibrate the aperture.
You should have the following 'bits'; 3 diaphragm unit retaining screws, 3 diaphragm unit assembly screws, 1 diaphragm base with coil spring, 1 diaphragm rotor, 6 aperture blades, 1 diaphragm cover. ( So you lost a blade ).
The reassembly of the diaphragm is self evident, just fit the leaf pins into the holes in the base and the rotor. You have to manipulate the 6th blade in order to get it into correct position. Fit cover plate and put in the 3 assembly screws. Connect the coil spring to the rotor pin.
Aperture Calibration. - all diameters in mm
f nos-----------------2.8-------5.6--------11
Upper limit-----------13.20-----6.48-------3.21
Reference value------12.07-----5.94-------2.94
Lower limit-----------11.04-----5.44-------2.60
The diameter is adjusted by loosening the retaining screws and moving the whole unit horizontally. Blades must be out of sight at f1.8 and check the f11 diameter after calibration, on the camera either with the stopdown lever or at B. |
Ben
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 16, 2006 - 06:44 pm: |
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Glenn,
Thanks for your reply. Are you sure about the number of aperture blades? I looked at my other(good) lens, and only counted five blades. When stopped down, they make a pentagon.
The three screws I removed were the only three I saw(and still see) to remove. I went in from the top, as Rick describes. I pried off the plastic name plate, removed the three screws under it, and lifted off the filter ring/hood bayonet. I(carefully) lifted out the front group as a unit, and there were the same three screws shown in Rick's diagram. These were the only screws I saw to remove, and there still are no others, even with the aperture disassembled.
Am I doing something wrong?
This is the earlier breech-lock version, and not the bayonet mount version.
Thanks again for the reply,
Ben |
rick
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 16, 2006 - 07:34 pm: |
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I don't have the 1.8 breechlock; my bayonet f/1.8 has 5 blades, and my breechlock f/1.4 has 8. i expect 5 is correct for your lens.
in both my 1.4 SSC and my 1.8 bayonet, there are only 3 screws visible and the diaphragm comes out as a unit. i haven't encountered a 50mm fd lens that didn't work this way, but it's certainly possible - your 1.8 might be earlier than my 1.4.
those aperture size values are very good to have. here's how i deal with that when i don't have specs to go by: i assume that the full aperture of the lens is accurate, and i divide the smallest aperture by the largest (for instance, 16 / 1.8 = 8.9). then i measure the diameter of the full aperture circle and divide it by this number to get the diameter of the smallest aperture. i adjust the lens at the smallest aperture and let the others float, because a given amount of error will have the most effect at the smallest aperture...
just for grins you might try checking this against the spec values that Glenn gave you - hopefully they would come in pretty close to the same. |
rick again
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 16, 2006 - 07:37 pm: |
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PS:
i would go ahead and remove the front element and get the fungus out as well as possible. if you catch it early you can prevent damage, but if you leave it in it will eventually become unrepairable as it etches into the glass.
also, it's easy enough to verify your blade count: count the pivot points on the mounting plate. |
Glenn Middleton
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 16, 2006 - 07:47 pm: |
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Ben,
Right you must have a very late 50/1.8 S.C. This is a 'bastard' lens - basically a new FD with the breech ring fitted. So ignore those setup figs, if I remember rightly there are some differences for this lens - will have to check later, manual not to hand.
Yes only 5 blades, so OK there. Do you have a front and back plate for the assembly? You must have the plate that was facing you as you removed the three screws, was there another plate loose under the rotor? Some doubts as to how the two plates are held together. Normally you have 2/3 screws and these can be fitted from the same side as the retaining screws or from the back. When fitted from the same side these screws are identified by a red varnish/seal on the heads or are in such a location that they cannot be mistaken - this depends on the exact type of lens. In this cheapo version perhaps the plates were a press fit or glued. I do wonder if the lens has been got at before. You will have to look for signs of extra screw holes or push fit pins. Are the two plates plastic?
The assembly method for the diaphragm is the same. As to how the assembly is held together, I do not know - this lens is not in any of my breech ring manuals and I only have the new FD 1.8 manual to work on. All the 1.8 lenses (breech or new) that I have worked on, have a diaphragm unit that lifts out complete and secure.
Sorry I cannot be more specific at moment. The Canon method of aperture adjustment requires a diaphragm unit with front and back plates. Why they are not held together by screws on your lens type I do not know. If you do not find extra screw holes it means that adhesive or a push fit was used. Come back with your findings.
Glenn. |
Ben
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 16, 2006 - 08:06 pm: |
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Glenn and Rick,
Thank you both for your help. I suppose the assumption that it's a late version breech lock matches up with what I know about it. It came with my A-1 that I bought off of Ebay, and my A-1 was date coded 1981. I've always thought it a bit strange that such a late camera didn't come packaged with a New FD lens, so I suppose that that's the explanation for it.
All that came out was the black plastic top plate. There's a shiney silver rotor attached to a spring that's still down in there somwhere. I attempted to lift the bottom plate out, but I couldn't get it to budge.
I'll pull out the digital(horrors!) and take some photos of it if it would help my explanation any.
Also, how would I go about separating the front element from the front cell? A rubber pad wrench? Also, do I need to mark it in some way so that I can correctly replace it?
Thanks,
Ben
Thanks again for the help! |
Ben
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 16, 2006 - 08:41 pm: |
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Okay, here are some pictures of what I'm dealing with
The first shows the inside of the lens barrel and the little silver rotor piece attached to a spring that goes somewhere deep down into the lens. To the right is the top retaining plate
http://im1.shutterfly.com/procserv/47b6dc37b3127cce971cb517cbb500000016108AcN2jNi0Yt7
The second photo shows the three scews I removed(top), the retaining plate(middle) and the 5 diaphragm blades(bottom)
http://im1.shutterfly.com/procserv/47b6dc37b3127cce971cb5144a8600000016108AcN2jNi0Yt7
I played around a little bit, and the best I can tell, the silver piece is supposed to go in the rim around the edge of the top plate, and then the diaphragm blades are placed on top of this assembly. The only problem is that that's going to be next to impossible with the spring attached, and it's going to be just as difficult to reattach the spring and keep everything in place. There has to be another way to go about this. I'm wondering if maybe I should try going in from the bottom. Or would that be asking for trouble also?
Thanks again,
Ben |
Ben
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, February 16, 2006 - 09:18 pm: |
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I think that I might have found a solution.
I took the bottom off, once again per Rick's excellent instructions, and I was able to unhook the spring and remove the silver piece. I can then(in theory) put the diaphragm back together, put it in the lens, and then reattach the spring. I'll see if I can do anything about adjusting the apertures, but as long as they're somewhere close, I may just let them fall where they wish and always use the lens with print film. I do have a very nice example to use with slides. |
Glenn Middleton
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, February 17, 2006 - 09:11 am: |
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Ben,
This lens is weird, because if that bottom plate is a permanent fixture assembly will be a pig. Also; if the three screws go through the 'bottom' plate into the barrel proper, you will have no adjustment on the aperture. Well not in Canon's accepted way of moving the diaphragm unit.
This lens could have taken cost cutting to the extreme and used adhesive to hold every thing together, however that needs a slow setting adhesive to let you position the diaphragm unit. You would have no guarantee that the unit would not move before it was secure.
I do wonder if the diaphragm unit is secured by 2/3 screws put in from the mount/rear end of the lens. Looking at the apparent diameter of the plate that has come out, I think that any calibration would be done by rotating the unit. This method is used on a number of FD lenses - you basically alter the amount of 'preload' in the linkage system. So are there some screws and/or little slots visible from the rear of the lens?
As to removing front element from front cell - sometimes the front element just sits in the cell and is retained by the filter/hood ring, proper slotted screwed rings can be used or the element is bonded/swaged/clipped into the cell. If the cell follows new FD construction, the element is a push fit into the moulded recess in the plastic cell and the lip clips the lens into place. You should not need to mark the position of the cell or lenses, but note the orientation of the rear group in the cell.
This type of lens was first marketed in 1976 and the new FD 1.8 in 1979. What is the date letter on the lens as a matter of interest? From observations - if prior to 1982 the lens and camera are within 3 months of each other, then the lens could be original to the camera. After 35mm slr production peaked in 1981 at approx 7.9 million, production fell rapidly with a 30+% fall by end of 1983. During this period camera /lens date correlation begins to unravel a bit.
Glenn |
Ben
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, February 17, 2006 - 12:56 pm: |
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Glenn,
Thanks again for your response. The screw holes in the plate that came out are slightly oblong. From playing with it last night, the entire assembly is rotated within the constraints of these oblong screw holes to adjust the diameter of the opening. I did actually get the diaphragm fully assembled a couple of times, however I think that's going to take trial and error to be able to correctly get it in the lens barrel. It has to go in exactly right on the first try, as rotating it any significant amount to line up the screw holes will cause you to lose one or two blades, and then you basically have to redo all of them. I did actually manage this one time, however as it turned out, I'd done something else wrong and it would only close down to about 5.6.
I took the mount off and was able to unhook the spring that's holding the silver rotor in place. This is how I've been assembling it, and once I get everything back in place and secured, I'll reattach the spring.
By the way, the date code is Q1207.
Thanks again for the help!
Ben |
Don
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, February 17, 2006 - 02:44 pm: |
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This sounds like the version I worked on some years back. It was the std. lens for the TX. I kept some notes that may be of help. Also have the SPT service info for same that may help. Can email the notes if you want. An easy way to measure diafram spacing is w/various size drill bits. A #44 is good for checking F16 on a 50mm lens & a 1/8 is pretty close (within tolerance) for F11. These #'s would increase slightly for a 55mm lens |
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