Canon LTM QL17 GIII: Adjust ASA to compensate for battery voltage

[anoldsock]

I just shot through a test roll with my Canonet QL17 GIII and I was really impressed with the quality of the lens. This might be sacrilegious to some, but I would almost dare to say that the Canonet may be easier to shoot with than the Leica IIIC.

Anyway, I've been reading up on the QL17 GIII about compensating for the increase in voltage for newer batteries. What I found is that people seem to adjust the ASA setting down a half step to compensate for the increase voltage.

Is this about right? I can't seem to find a definitive answer, Is there a guide for this out there somewhere?

 

[payasam]

If you can find a silver oxide (1.55V) cell that fits exactly, a bit of experimentation should tell you how much you need to compensate. Its output will be constant, like that of a mercury cell. The alkaline 625 cell (the right size) will be a problem, because its output slopes down through its life and compensation will need to follow.

 

[Sonnar Brian]

It's about right. The voltage discharge on alkaline batteries is not as smooth as mercury cell. Silver Oxide batteries are a bit better. I've been using MS-76 silver-oxide batteries.
Comparing the same camera using an original Mercury Cell vs a 1.5v battery, I adjust down 1/2 stop.

 

[nzeeman]

i put 320 asa if i use 400 asa film. i think i get good exposures.

 

[saltyfli]

Replacing your old mercury battery

Replacing your old mercury battery

Why not just buy the Cris MR-9 battery adapter? Never worry about it again. I have used this adapter on all older Canon equipment which used the mercury batteries and never had a problem.

 

[Ronald_H]

My GIII came with a alkaline replacement.

I shot FP4+ at 250 and developed in Diafine. 250 is the recommended rating for Diafine & FP4+, BUT for Tri-X it's 1600 and I'm happier at 1250.

The negs looked a bit underexposed, but that's it, only a bit. They scanned very well and should be no problem to print either. IMHO sticking to the normal ISO setting will hardly ever cause problems with negative film.

If you plan to use slides, try a reference meter to see how much the Canon is off, then adjust ISO as needed.

 

[Kim Coxon]

Sorry to be awkward but adjusting the ASA is not a good solution unless using wide latitude film. The resistance of the light sensor is not linear. At the bottm EV's the meter will be very close even with a silver cell. However in bright conditions, it can be nearly 2 stops out. If you just adjust the ASA, it will only be accurate at a certain light level. If you use one stop, it should be alright in the middle but will be about a stop out at either end. The most effective solution I have found is to adjust the meter.

If you take the top off, the adjustment pot is just behind the film moving flag. On a bright day, adjust this so that the meter reads the same as a handheld and it should be accurate to about a half stop acroos the range. If you need it more accurate than this, it can be down but the meter mech needs to be adjusted in it's holder.

Kim