Canon Serenar 50mm f1.8 focus off

S

superultramega

Established
Local time
10:52 AM
Joined
Sep 4, 2007
Messages
61
I bought this lens almost a year ago and have not used it very frequently. I've known the focus was off for some time but today I put it on a tripod and shot a focus chart. Well the focus point is 8 to 10 inches to the front of the target. :eek: Is this a repair that I can consider doing myself?

Thanks
 
Could you tell us what model Rangefinder Camera your using?. Is this your only rangefinder lens that your seeing this problem with the camera your using? My Canon 50 1.8 will only focus down to approx. 3.5 ft without a close focusing device in front. I see now when looking more closely that your lens will only focus down to 1 m.
 
I would suggest that one of the more common reasons for this problem (if it is indeed the lens and not the camera) is that someone has serviced the lens but in doing so has reassembled the helical wrongly. These things have to be screwed back together in exactly the right way otherwise the focus will be off. Its an easy problem to cause but once done it can be a pain to fix as if indeed it is this problem, it needs trial and error to get it right again. Unless, as sometimes is the case, there is an indexing mark scratched on the helical threads where they join. This mark shows how the helicals must be realigned once they have been separated. If someone did not do this there are many ways of reassembling the lens. Only one of which is the correct way. Anyway that is supposition but it is a reasonable possibility.
 
It's an ltm lens. Are you using it on an M mount body with an adapter?
Adapters are highly suspect when focus issues come up.
Most cheap ones are nearly worthless.
The voigtlander ones are best and worth the investment imo..
 
f16sunshine said:
It's an ltm lens. Are you using it on an M mount body with an adapter?
Adapters are highly suspect when focus issues come up.
Most cheap ones are nearly worthless.
The voigtlander ones are best and worth the investment imo..
Click to expand...

Totally agree with what you stated. As per my 1st reply, I wanted to know "what kind of Rangefinder" he was using. Peter also made some very good comments too; but my suspicions are more with an older camera that has not seen any service by a qualified tech.
 
superultramega said:
I bought this lens almost a year ago and have not used it very frequently. I've known the focus was off for some time but today I put it on a tripod and shot a focus chart. Well the focus point is 8 to 10 inches to the front of the target. :eek: Is this a repair that I can consider doing myself?

Thanks
Click to expand...

At what distance is it 10 inches off? Do the RF images converge properly at infinity, and if so are shots at infinity properly focused? Finally, when focused close, do the RF convergence and the focus scale say the same thing. Usually I don't believe focus scales, but 10 inches is enough off that this is meaningful data.
 
Thanks everyone for the responses and questions. This is my first experience with a mis-focusing lens so I've clumsily been working through testing it. The focus test yesterday was on a Bessa R, I also tested a Voigtlander 50/1.5. The Canon lens showed missed focus while the Voigtlander did not. Ten inches was at roughly 4 feet. It was also off at 8 feet. I haven't made prints yet so it's had to tell how far off the focus is exactly.

I think the testing done yesterday proves the problem is with the lens. But I first noticed the focusing issues while using with a Canon P. I did some informal testing with the P and both lenses again it seemed to be the Canon lens was off while the Voigtlander was good. I also compared the Bessa/Voigtlander combination to the Canon/Canon focusing on items around my apartment and comparing the indicated distance on the lens and they seemed to be the same. Or close to the same considering small differences in my body placement.

So if the problem is the lens the repair is a difficult one? I purchased the lens locally can I go to the seller and ask them to take back the lens or offer a discount or for help in repairing the lens? Not sure if this is inappropriate after 6 months of ownership. I like the build quality and handling of the lens but shooting infinity at f8 can be limiting.

Thanks
 
It does sound like the lens. Returning after 6months is probably not cool but.. you can try.
DAG or focal point for tuning it.
DAG has been very reasonable to do so for me in the past. Still you are likely going to pay $75-$125 to have this lens adjusted.
You could search the googlzweb for tutorials on how to do so yourself.
Good luck. It's a nice lens!
 
In principle this is usually not difficult for a qualified professional to do. Typically a CLA of this sort will cost me around $100-$150, depending wholly on how much time the tech spends on it. If I do it myself, I find dis assembly (or more to the point reassembly) of lenses a challenging thing to do as there are so many small parts which have to come apart in the correct sequence and go together again not just in the right place but in the right sequence. I do not like doing it myself as so much can go wrong if you do not know what to do and are learning on the job with no one to advise you. Having said that I have always managed to get it right (eventually). Also a few specialised tools are needed like special spanner wrenches and some glass lens elements can be confusing as to which is the front and which are the back of the elements - causing potential problems for reassembly unless you carefully mark everything and keep a record of what you did in which order. Photos as you go are a good idea. All in all it is something I prefer to pay to have done professionally if it involves a complete breakdown and dis assembly of a lens. A lens element cleaning is simpler usually but even it has its challenges for a newbee. Your problem in this case will be in knowing what is causing the issue is once the lens has been disassembled. You will still be in the dark as the problem is unlikely to be obvious unless you know exactly what to look for. And that is where the knowledge of a pro comes in. BTW one other area that causes focus issues (back focus more than front focus usually) are the small brass collars or shims that help position the focusing unit correctly. Usually one or more shims are used by the factory as required to bring the lens within tolerance. If there are focusing problems more often, a shim has gone missing and that causes back focusing of the lens. In your case it is unlikely an extra shim has been added to cause front focusing but I would carefully want to check their position and the collimation of individual lens elements to make sure all are positioned correctly and locked down and centred. Having said all of that I am an amateur not a pro so feel free to ignore everything I say. :^)

The following video will give you a rough idea of what is involved, but its only an idea, as the lens in this video is both a different lens (LTM Canon 50mm f1.4) and a later model so the all important details may be similar but definitely will be different.

https://www.youtube.com/watch?v=qMRnqIysGAk

The following article which relates specifically to your lens also provides some idea of what is involved in disassembling and cleaning the lens elements (but not adjusting focus) so this does not go as far as you most likely need. Never the less you may find it instructive if youa re inclined to take a peak inside the guts of your lens.

http://jelabs.blogspot.com.au/2011/04/canon-serenar-f18-50mm-ltm-lens.html
 
This problem happened to me, with a later version of the same lens, a Canon 50/1.8 LTM I got on eBaaay, and then had CLA'd. First I thought I was crazy. I set up a test using a tape measure, little paper flags, a tripod and careful recording of the lens markings, then did a systematic focus test. With paper flags at every 6 inches, i was able to compare where I thought the lens was focused with where it actually focused. The problem was either the lens as it came from the 'Bay, or with the reassembly after the CLA. Since my CLA guy did not have a collimator--an instrument necessary to measure proper alignment of elements within the lens barrel--I had to send it a guy in Atlanta (I'll look for his name somewhere later if you like) who is better known for rebuilding Yashica TLRs, who also worked on Canon lenses of the era. All in all, I spent $250 rebuilding a $200 lens, and then sold it at a loss after a friend gave me a very nice Canon 50/1.4. But I felt better knowing I had rehabilitated a nice piece of equipment for the future use of some rangefinder aficionado.
 
An old article on lens collimation. Albeit on a Super 8mm camera. But the principle is exactly the same for all optical systems. This is part of what the technician needs to do and hopefully he will have a collimator to use in the process. (I steered clear of this stuff in the original post as its a bit technical, but as someone else has raised it.............)


http://www.oocities.org/sunsetstrip/studio/4474/lenscollimation.html

I think with cameras that have a back which opens it is also possible to use a ground glass screen placed where the film would normally be to help in the adjustment process. This way it is possible to see if the image is focused when it should be and allow adjustment of the lens accordingly. Not sure how this would be achieved with LTM type cameras which do not have an opening back unless it can be done by removing the camera case. In any event probably beyond what most amateurs would aspire to.

And there is a bit more useful practical advice and theory here.

http://lens-club.ru/public/files/pdfs/c538ad9a97e8164d56c1d17eb68378b1.pdf

also here

http://elekm.net/zeiss-ikon/repair/collimate/

All I can say though is that while I find it kinda interesting in a geeky kind of way its way beyond my pay grade to actually do it. Which is why I prefer to pay the money and let someone who actually knows what theya re doing undertake the work.
 
Hi,

8-10 inches is way toooooo much!

That kind of problem must mean the lens has the main shim gone. Or it was poorly assembled at some point (not canon problem)

I can say the 50mm f1.8 is so good that even doesn´t have focus shift.

I´ve just sold mine because never liked the black/alum. But i plan to get me the chrome version. They are still quite inexpensive!!!

Good luck!
 
Monochrom said:
Hi,

8-10 inches is way toooooo much!

That kind of problem must mean the lens has the main shim gone. Or it was poorly assembled at some point (not canon problem)

I can say the 50mm f1.8 is so good that even doesn´t have focus shift.

I´ve just sold mine because never liked the black/alum. But i plan to get me the chrome version. They are still quite inexpensive!!!

Good luck!
Click to expand...
Being a early and present Leica owner, the blk/alum. 50 1.8 is every bit as good as my early 50 chron's. Used on my "f's" and "z" body this lens is a standout for me.
 
Thanks for the technical links but I think this is something that I am fully capable of ruining completely if I attempt a repair. I'll be calling Focal Point and depending on the quote a Canon 50mm may be in the classified soon. The metal is in fair/good condition and the glass is haze and scratch free.
 
Happy ending! I took the lens to the shop and the owner had the lens repaired. Turns out one of the elements had been placed in backwards. Tech said this is a particularly sharp copy. He also cleaned the elements, and the aperture ring is no longer stiff. Great customer service and now I have a fantastic version of a lens whose handling I really enjoy. If anyone is in San Francisco and wants to go to a highly recommended film only camera store please check out Glass Key Photo.
 
I love happy endings. These are great lenses. Now you need to look for a Canon 100mm f3.5 and a Canon 28mm f3.5 and you'll have a wonderful, small kit. Joe
 
You must log in or register to reply here.
Back
Top Bottom