How to set ISO compensation when using a 1.5V battery on a 1.35V M5?

[roundg]

My chrome M5 arrived yesterday. I put a 1.5 V 625 battery in it and since m5 uses 1.35 V battery. I use ISO dial to do the compensation, that is, set to 100 with a ISO400 film.

I compare the metering value with my another M5 which has the circuit modified for 1.5V battery, and found they were quite close.

How do u compensate with the 1.35V M5? and what's the result?

 

[Spyderman]

I cannot speak for M5, but a similar problem 1.35 vs. 1.5 is also on OM-1.

The error in OM-1 is not linear, thus it cannot be compensated for by changing the film speed setting. The error is different in low light and in bright light...

Just buy an adapter which drops the voltage as well as physically adapts the AgO cell into the battery compartment.

 

[Ray Nalley]

Or just use Wein cells. The MR-9 adapter also works well, but I usually just use Wein cells these days.

 

[venchka]

What Ray said. Wein cells work. Be sure to leave the shutter uncocked and thereby conserve the battery.

 

[Vincenzo Maielli]

The alkaline battery V625 show an inconstant curve of discharge in her life: at beginning is 1,5 voltage, in the middle is 1,4/1,35 voltage and when the battery is discharged is 1,1 voltage. This circumstance oblige you at an exhausting, hard, continuous and substantially useless work of compensation (a true Sysiphus fatigue's). Although this solution is scarcely sufficient for the colour or BW negatives, is very bad for the colour slides, that request the maximum precision in the light measurement. The silver oxide batteries, in the contrary, are very stable and constant in their curve of discharged, exactly as the PX625 mercury oxide batteries.
In my Leica M5 i use an MR-9 adapter, that permit the employ of a 386 silver oxide battery. A micro electronical circuit, inside the MR-9 adapter, automatically reduce the 1,55 voltage of the 386 silver oxide battery into the 1,35 voltage, as request from the meter of the M5 (the MR-9 work perfectly good in all my cameras the request the longtime outlawed PX625 batteries, except in my Leicameter MR).
The MR-9 adapter, made by japanese Kanto, is selled from the Cris Camera Service, in USA, or The Small Battery Company, in UK.
Another good solution is the employ of the SPX625 silver oxide battery, to replace the PX625 battery: the dimensions are the same in both the summentioned batteries and the same constant curve of discharge give possible the ISO compensation with all the available films. Also the SPX625 is simply to find both in USA and UK (at The Small Battery Company).
I find that the MR-9 or SPX625 silver oxide are both better solutions than the Wein Cell MRB625 zinc air batteries (that not allow a very good time duration).
Ciao.
Vincenzo

 

[roundg]

Thanks for all inputs. Really appreciate.

I have put one roll inside and to see how will be the result by setting ISO 100 instead of 400 (the speed of the film is 400)

I will buying some 1.35V battery as suggested. Thanks that u have listed all type and details about them, especially thank Vincenzo for the performance compare.

My another M5 had its metering modified to use 1.5V battery. It's very accurate with negtive and slides. Actually my first thought is to send the new M5 to DAG for a same modification but the turnaround is too long for me.

BTW, the meter on the m5 is the best I ever see on a camera. Very accurate and user friendly.

Cheers,