Canon LTM GIII QL17 : Aperture problems in A mode

Canon M39 M39 screw mount bodies/lenses
I spent my afternoon to peek more inside the camera, and i can't find i try to tighten the screws of the meter/needle, i now need some new leather because i open the face plate, and i still can't find the piece.
I think it's just a little adjustment.I've find some info on the web about this problem but i can't find wich is the piece i need to adjust.

"Yes, the position of the galvanometer needle is detected by the sagged blade which swivels in front of it as you depress the shutter button, and transferred to the aperture coupling mechanism. Only thing to adjust here is the fully opened aperture. When the needle points at f/1.7, of course the aperture should be fully opened, and the aperture blades should be barely visible through the lens opening. This adjustment (only if necessary) is done by bending a lever in the transfer mechanism. It can be fine tuned by turning a screw with excentric head which links the swivelling blade to the mechanism."

i can't locate that lever.:bang:
 
Thanks grayhoundman - I never realized that. I thought it was just some electrical problem...

I think I'll have to dive into the depth of Canonet repairs once again... last time it was some year and a half ago to clean the shutter blades...
 
Tip of white arrow is the adjustment you are talking about. It is just under the dark colored bar. You can push down the shutter release and see it clearly.

Photo belongs to Rick Oleson.

Be careful what you mess with. You could end up with a doorstop.
 

Attachments

  • canonet2.jpg
    canonet2.jpg
    107.5 KB · Views: 0
Thanks a lot greyhoundman!
i got that piece in my hand earlier,but i wasn't sure, it looks more simple now, it's the piece with the spring.
Thanks again.
 
I bent it, and tried and tried...
And everytime i come close to the good aperture, i lose the manual mode because
of the mecanism that lock the shutter when there' s not enough light.
I tried to bend a litlle more each time,now everything seems almost ok, i think i've bend the needle too but i'll set it right.
It was really a hard job, i spent hours on it.
 
Interesting discusson. I just found some older thread here concerning calibrating Canonet QL-17 G-III to meter with 1600 ASA films. User drm suggest both mechanical adjustment of metering mechanism and adjustment of potentiometer.

Whole post is here: http://www.rangefinderforum.com/forums/showpost.php?p=390669&postcount=17

Is it sane and safe or rather not? I'm tempted to try but I don't want to end as Fabrice2 with camera malfunction...
 
Oscar Wildes advise to those about to be married applies...

Dont...

If you are using >800 invest in a photo meter, if you need fast film the shutter lock in the red is too exposed anyway.

Noel
 
A mode means automatic doesn't it? Why would you adjust the aperature in A mode? As I remember, the aperature automatically goes to the right setting when you shoot. I'm not sure that I understand your problem exactly, but I remember puzzling about this myself.
 
Well the problem is, that the lightmeter in G-III is generaly inreliable (due to it's age, field of view and much worse use of 1,5V batteries). Yes, I can use manual mode, but I want to use auto and want to have it accurate as much as possible. I think this is nothing to be misunderstood.

The thread I linked suggest adjustments to calibrate lightmeter pretty well, but as there is not much feedback I would like to ask somebody other familiar with Canonet's mechanics.

The possibility to calibrate meter to work accurately with ASA 1600 I just consider very handy.

User drm in the linked post suggest this procedure:

1. Disassemble the top part of the Canon.

2. Set the Canon ASA/ISO to 200, corresponding to ISO 400 film.

3. Mechanically adjust the meter on the Canon so the meter indicates
f2.8 to agree with the Pentax using the low light test source.

4. Electrically adjust the meter on the Canon so the meter agrees with
the Pentax using the bright light test source.

5. If necessary, repeat steps 3 and 4 as required.

6. Re-assemble and shoot test rolls.

see whole post: http://www.rangefinderforum.com/forums/showpost.php?p=390669&postcount=17

I have no problem with adjusting a potentiometer (point 4). But I hesitate to proceed to point 3 which means mechanical swiveling with the barrel of metering assembly. First I was eager to try it, but after I red the greyhounds remarks about trap metering and fabricius2 problem I'm mores suspicious. I would like to ask, especially greyhound, if the metering adjustment proposed in the linked thread is not just the method how-to create such metering trap?
 
I'm sure it is possible and DMR will appear and is helpful, but customising your toy is risky, and will take time.

If you use a new battery (Alkaline or AgO or even a old AgO) and have not adjusted the meter or used a voltage dropping diode the metering will be close to 800 asa if you set it to 400 anyway!

I normally set mine 2/3 stop slower than the film package to compensate for the higher voltage. A problem when I use 25asa film.

Noel

P.S. my metering and shutter seem reliable.
 
Thanks for your response!

Actually my camera was adjusted to new alkaline batteries by expert mechanic - former owner told me. But some problems apparently persist, I don't know exactly why. First I experienced underxposures (1-1.5 EV) when photographing in bright light conditions. Pretty high number of shots was lost due to (unreasonable) exposure lock. In normal or dim light conditions the metering was quiet accurate.

So I dissasmbled top of the camera and played with potentiometer for a while. Now I have quiet exact exposure readings in bright and normal light, but getting between 0.5 - 1 EV overexposure in dim light. This is not much bothering as I employ pretty effective staining development, but unfortunately sometimes the image is lost due to exposure lock again .

So you see that as the metering error is not really constant, the adjustment of ISO ring is unfortunately not the solution of my problem.

Actually before I realized problem I photographed good number of films and generally was getting good photographs. But some images was not exposed correctly without apparent reason so I began to be suspicious. And now looking for solution...
 
Last edited:
Some people can ignore the needle and it is annoying when the button wont budge. I use the other eye and dont see the needle, that is I keep both eyes open, but the left dominates. It really annoys when I leave the hood cap on.

But it looks like the meter is non linear, a proper fix would have kept it linear. I still have Hg0 cells, but when they are done it is a point contact diode.

Noel
 
The "expert" probably moved the meter in it's mount. Then you "adjusted" the resistor.
It is now out in a way that will require a lot of testing to cure.
 
A good excuse to linerise and recalibrate, it for 1600 if you wanna be brave.

I'd fit a Shokkey diode in circuit first and buy a AgO battery, then the fun starts, grey dog person will help...

Noel
 
Hmm, in fact I don't think the metering is so much messed up now. I'm just getting f1.7 when the f2 would be OK and exposure lock when f1.7 would be sufficient. It could be nearly called feature 🙂

Well but seriously, can you suggest me something? What about the calibration suggested by DRM in the linked thread above? Or where to began? What exactly means to "move meter in the mount"?
 
You must log in or register to reply here.
Back
Top Bottom