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Can anyone tell me what is missing from this lens?
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PostPosted: Sat Jul 21, 2012 8:11 am    Post subject: Can anyone tell me what is missing from this lens? Reply with quote
Hi all,

Im thinking of bidding on this dissembled vintage Cannon 58mm f1:1.2 lens for use with an upcoming 3 stage cascade NV spotter scope project, it is listed as 'spares or repair' but not having much knowledge of lenses in general was wondering if anyone can tell me there are any individual lenses or parts missing from it?... and if its just the focus ring that is detatched how would I re-attach it?

The item number is 110914003380 on that popular auction site which It seems I am not allowed to link to..

Thanks,

Paul


PostPosted: Sat Jul 21, 2012 8:28 am    Post subject: Reply with quote
Link to item.
Click here to see on Ebay


PostPosted: Sat Jul 21, 2012 8:35 am    Post subject: Reply with quote
Thanks Walter.

Smile


PostPosted: Sat Jul 21, 2012 11:10 am    Post subject: Reply with quote
Looks like the optical block is complete, but it also looks like it's missing parts.
+ this
Quote:
The glass has some sort of blemish like a chip or nick at the very edge of one of the inside elements
from the q&a


PostPosted: Sat Jul 21, 2012 1:10 pm    Post subject: Reply with quote
The lens is definitely missing parts. For example, compare the mount part with this picture from http://www.mir.com.my/rb/photography/companies/canon/fdresources/fllenses/FL85mmf18_B.jpg:


As you see, the cover is missing. Assume that the aperture control mechanism is missing too as it is behind the missing cover and I don't see aperture control lever included. I've never disassembled an FL lens, good FD lenses have a bunch of ball bearings behind similar cover.

The lens block along should be worth more than 20 pounds though, but what will you do with it without the spare barrel? I don't think you can source replacement parts from cheap FL 50/1.8, as the sizes are different.


PostPosted: Sat Jul 21, 2012 3:45 pm    Post subject: Reply with quote
Thanks Lightshow, yes I had seen the Q/A comment but a nick doesn't really worry me.


fermy wrote:
The lens is definitely missing parts. For example, compare the mount part with this picture from http://www.mir.com.my/rb/photography/companies/canon/fdresources/fllenses/FL85mmf18_B.jpg:


As you see, the cover is missing. Assume that the aperture control mechanism is missing too as it is behind the missing cover and I don't see aperture control lever included. I've never disassembled an FL lens, good FD lenses have a bunch of ball bearings behind similar cover.

The lens block along should be worth more than 20 pounds though, but what will you do with it without the spare barrel? I don't think you can source replacement parts from cheap FL 50/1.8, as the sizes are different.


Thanks Fermy, thats very helpful.

Does it look like the focus mech is still intact? Although I wouldn't need an aperture for my project I would need a focusing mechanism and also a way to mount it to a tube/pipe cap. So if it isn't ntact it doesn't look very feasible.. a pity as something as fast as F1:1.2 would be a great basis for the NV scope project.
I'll just need to keep looking and may just settle for a 50mm F1:1.4 or maybe even a 135mm F1:2.8 if I decide to attach a 300mw IR laser Illuminator.

Thanks for the input guys, I apreciate it.

Smile


PostPosted: Sat Jul 21, 2012 4:04 pm    Post subject: Reply with quote
The helicoid might be in place, it's hard for me to tell.

However, this is a bad lens for a scope. It has a thorium glass, which is low radioactive. It's relatively safe, however human retina is much more vulnerable than the skin and the rest of the body. So peering into the lens for prolonged periods of time without any shield between you and the lens is not recommended.


PostPosted: Sat Jul 21, 2012 4:04 pm    Post subject: Reply with quote
The aperture is in the optical block so that's intact. However, the focus mechanism looks like it's destroyed, I have stripped down an FL 2.5/35 before and it is constructed the same. I think this FL 1.2/55 should just be considered an optical block in need of remounting in a new helicoid as the original one looks destroyed and half of it missing.


PostPosted: Sat Jul 21, 2012 4:42 pm    Post subject: Reply with quote
fermy wrote:
The helicoid might be in place, it's hard for me to tell.

However, this is a bad lens for a scope. It has a thorium glass, which is low radioactive. It's relatively safe, however human retina is much more vulnerable than the skin and the rest of the body. So peering into the lens for prolonged periods of time without any shield between you and the lens is not recommended.


Thanks, thats interesting.. I wasn't aware of that. What sort of radiation levels are we talking about? Would it still be a danger when there would be a 25-30cm (ish) long 3 stage cascade image intensifier tube (plus an oculer) between the lens and my eye?


PostPosted: Sat Jul 21, 2012 5:04 pm    Post subject: Reply with quote
Ari33 wrote:
Would it still be a danger when there would be a 25-30cm (ish) long 3 stage cascade image intensifier tube (plus an oculer) between the lens and my eye?


I don't think so. That would block most of alpha particles plus reduce the level dramatically due to distance.

http://answers.yahoo.com/question/index?qid=20081203045300AAozSaH

Quote:
Measurements gave up to 5.85 μSV/h for the lens measured from the rear element, which is quite much!!


PostPosted: Sat Jul 21, 2012 5:27 pm    Post subject: Reply with quote
The radiation levels are nothing to worry about unless you press the lend against your body for days on end.
http://www.hps.org/publicinformation/ate/q1356.html

Quote:
Thorium emits alpha, beta, and gamma radiation. For cameras employing thoriated lenses, only the gamma rays result in a dose to the lens of the eye (or any other part of the body for that matter).

The major determinant of the dose to the lens of the eye is the length of time the photographer is holding the camera up to the head. As an example, the dose rate near the viewfinder of an old Pentax camera of mine (Super Takumar lens) is roughly 100 microrad per hour—approximately ten times background. In other words, looking through the viewfinder of this camera for one minute results in the same dose that I receive every ten minutes when not using it. I would have to hold this camera up to my eye for several million hours to exceed the threshold dose for cataracts. .


PostPosted: Sat Jul 21, 2012 6:01 pm    Post subject: Reply with quote
This forum really is a great source of information, I can see myself coming here quite often.

Thanks guys.

Smile


PostPosted: Sat Jul 21, 2012 10:08 pm    Post subject: Reply with quote
It went for 37.61. Thought I'd won but some asshole sniped it with 1 sec to go.


PostPosted: Sun Jul 22, 2012 8:40 am    Post subject: Reply with quote
iangreenhalgh1 wrote:
It went for 37.61. Thought I'd won but some asshole sniped it with 1 sec to go.



...wasn't me!

Smile
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