Y.A.S.C. (Yet Another Canonet Story)

[nzeeman]

navdra thanks a lot - this is first time i saw this thread - i dont know how i missed it until now. great help for all canonet users!!

can we make this one sticky?

 

[dmr]

About the battery, I'm not much of a tech guy, I don't fully understand how the meter works and I've heard all kinds of versions on how to work with higher voltage cell. I'm just going to compare Canonet's metering with my other camera's metering and make the propper adjustments.

You will hear more opinions on this topic! There are all kinds of work-arounds, from very simple to very traumatic.

A couple years ago I was able to recalibrate the GIII to use both the newer "wrong" battery and 1600 ASA/ISO film. Here's the long-forgotten thread:

http://www.rangefinderforum.com/forums/showthread.php?t=25305

I'll consider buying Jon Goodman's kit but for now I'm just going to look for something in local stores.

I would also recommend Jon's kit. Everything fits just fine. Getting the old seals out is the messy part! I don't think a similar kit is sold in stores anywhere.

 

[cristin]

Thanks for the info, dmr. I'll see what I can learn form there.

 

[FallisPhoto]

No, you understand wrong. The problem with higher voltage won't be linear throughout EV levels, meaning that in low light conditions meter with 1.5V battery inside will show good exposure (if set properly for 1.35V), but in higher EV levels it will cause overexposure (even 2-3 stops). This circuit is very simple: battery - resistor (cds cell) - galvanometer (light meter with needle). There is probably variable resistor added next to light meter for linearity adjustment too. When light levels go up, CDS cell lowers it's resistance and causes voltage difference in battery source to have higher impact on meter reading. That's how I look at it. So, no Alkaline, no silver-oxide..
Anyway, see for yourself. Go out and point camera to area that will show 1/125s and f/4 with 100 ASA film speed. When you adjust shutter speed to 1/15s it should read f/11 and with 1/500s it should read f/2. With alkaline inside, it won't happen.
If you want to read further on this matter, here is very good source:
http://www.buhla.de/Foto/batt-adapt-US.pdf

What you need to do is get 675 hearing aid battery and adapter to place it inside PX625 compartment.
After you do that, you can check if variable resistor needs adjustment. This is the best solution, if accuracy is priority, which I believe should be.

Actually, if you don't want to use the zinc-air hearing aid batteries, you can use a silver oxide battery, but you would need to solder in a 1N6263 Schottky diode, in series with the battery. Alternatively, you can get an MR9 adapter (which already has the diode). http://images.google.com/imgres?imgurl=http://www.smallbattery.company.org.uk/sbc_mr9.JPG&imgrefurl=http://www.smallbattery.company.org.uk/sbc_mr9_adapter.htm&h=251&w=251&sz=17&hl=en&start=7&um=1&tbnid=ebeFC9h8DXMosM:&tbnh=111&tbnw=111&prev=/images%3Fq%3D625%2Bwein%2Bcell%2Bcanonet%26um%3D1%26hl%3Den%26sa%3DG Metering and exposure will work fine, but the battery check light on a GIII QL-17 or QL-19 won't work.

If you do decide to use a #675 zinc-air battery, then an old and completely discharged #625 Wein Cell makes a handy adapter. If you really look at a #625 Wein Cell, you will see that it consists of a 675 battery press-fitted into a 625 shell. Dig out the 675 battery, ream the shell just a bit, so you don't have to put the new 675 battery into it with a hammer, and you have an adapter.