Help me with a battery voltage question

[boarini2003]

Okay, I want to know something. I just got a Canon FTBn SLR for my girlfriend. I didn't find the 1.35 volt battery to replace the dead one that came with it, so I got a 1.5. The meter is working, although the reading is 3 stops above what it should be. I compensate by lying to the camera throught setting the ISO 3 stops lower. Here are my questions:

1. Could this meter discrepancy be due to my using the wrong voltage?
2. Is it okay to use a battery that's 0.2 volts over the recommended battery?

Thanks!

 

[bmattock]

1. Could this meter discrepancy be due to my using the wrong voltage?
2. Is it okay to use a battery that's 0.2 volts over the recommended battery?

1) Yes.
2) Yes. You have to do just what you're doing, however.

However, you probably want to use a battery that is closer to the original voltage. Several ways to do this. You are about to receive all kinds of posts to this thread explaining how. You can't get the original battery, by the way, because it is made with mercury and that sort was outlawed.

Best Regards,

Bill Mattocks

 

[Goodyear]

2) Yes. You have to do just what you're doing, however.

Something I've wondered: will the response be linear across the EV range?

IOW, will the adjustment by candlelight be the same as the adjustment on a sunny beach?

/edit: 'uniform' would be a better word than 'linear', wouldn't it...

 

[bmattock]

Something I've wondered: will the response be linear across the EV range?

IOW, will the adjustment by candlelight be the same as the adjustment on a sunny beach?

/edit: 'uniform' would be a better word than 'linear', wouldn't it...

No, it will not be uniform. I have found by experience (not by being an electronics whiz, which I ain't) that I have to compare the meter to a known good source and make an offsetting adjustment for varyious lighting environments.

For this reason, I tend not to use an internal meter in a vintage camera unless I have some particularly good reason to do so, such as the camera has no manual mode (Electro GSN) or I just plain believe in it. A modern external meter is an excellent companion to most vintage cameras.

Best Regards,

Bill Mattocks

 

[Goodyear]

That was my suspicion. And the reason I sprung for Wein cells for my Lunasix...

 

[remrf]

I don't know about the Cannon series but a friend had some Nikons that used a mercury battery and he sent them to a tech who recalibrated the meter to the new voltage. When he got them back they were spot on compared to his Gossen Luna pro. Might be worth a google to see if someone does the same for Cannon.

 

[bmattock]

I don't know about the Cannon series but a friend had some Nikons that used a mercury battery and he sent them to a tech who recalibrated the meter to the new voltage. When he got them back they were spot on compared to his Gossen Luna pro. Might be worth a google to see if someone does the same for Cannon.

The problem is not that the meters cannot be recalibrated - they can. The problem is that mercury batteries were very, very stable. They put out their rated voltage from birth to very near death. Alkaline batteries put out more than their rated voltage for a brief period of time, then drop in a fairly steady manner, but then they fall off a cliff quite some time before they die. Silver oxide batteries are a tad bit more flat in their response - better than alkaline, worse than mercury. Zinc-air batteries (Wein, hearing aid batteries) put out the correct voltage and they are very stable in their output, but they don't last as long as alkaline or silver oxide batteries, and they can cost more. Still, they may be the best way to go in terms of a mercury replacement.

Best Regards,

Bill Mattocks

 

[T_om]

Go with hearing aid batteries.

Tom

 

[bmattock]

Go with hearing aid batteries.

Tom

Hearing aid batteries have the additional problem of not being available in the size used by the Canon FTb and FTbN. Some have used them anyway, but have filled in the empty space around them with a cardboard tube, aluminum foil, and so on.

There are also adapters available that step down the voltage of an alkaline or silver oxide to the correct voltage and provide voltage regulation to keep output straight-line.

No matter what - on a vintage camera, the meter is vintage as well. In my opinion, it is therefore untrustworthy. Essentially an electro-chemical reaction based on a sensor known to go bad after a period of time, I don't understand why folks don't simply use an external meter - it is simplicity itself. But to each their own.

Best Regards,

Bill Mattocks

 

[ErnestoJL]

From the experience I had with old cameras, there are several ways to solve the problem, however I think (and it´s just my opinion) the best is to have a good HH meter anytime you need it (as Bill said previously)(and his advice is perhaps the best solution you would ever have).

The main problem resides in which type of meter does the camera have: if it´s of the bridge type, the problem exists, however it won´t be quite serious as the battery voltage will only reduce the gap between under and over exposure marks in the VF.

If the meter is of the series type, then the only way to solve it either recalibrate the meter (and perhaps modify the electrical circuit) by a competent tech, or use the right batt voltage.

Examples: My Miranda Sensomat meter is right on spot after starting using silever oxide cells which don´t last as long as the original mercury types (see voltage drop by age curves). My Canonet meter didn´t react the same way so I added a small Schottky diode to drop the extra 0.2 V brought by the battery. Then everything was again OK.

Ernesto

 

[remrf]

I'm using a 6vdc battery in the Yashica Electro 35 with a straight through adapter. The original voltage was 5.5 I think. I read in more than one location on a google search that it did not seem to make much if any difference as to the accuracy of the metering. The negatives I've scanned from the camera seemed to be properly exposed.

However: The last time I went night shooting with the Yashica I took along my Luna Star F meter as well and the camera was computing the exposure at f-22 (400 asa) at about a third less time than indicated by the external meter. The negatives from this roll using the internal meter looked just as evenly exposed as my previous night shoot where I used the external meter exclusively. The Luna Star F by the way agrees perfectly with my spot meter and a friends Luna Digi 6.

I'm going to alter my adapter to accept a diode which will drop the voltage. As I look around the web I don't see a diode that will hit the mark spot on but it will be interesting to see if there is a proportional change in the metering as compared to the external meter with even a .2 drop. As has been mentioned the voltage should produce a flatter output line over time in any case.

 

[wlewisiii]

I think that the most important thing with any meter is if it is consistant. You can get used to the quirks of a meter that is 5 stops off - if it is allways consistantly so. With any meter that is new to you - handheld or in a camera - you need to get used to it and to learn if it is consistant in similar light situations. I get good results out of my old meters, but I've made sure I know what to expect from them and (since 99% are selenium) not to use them in too dim of light.

As with everything photographic, practice your metering.

William