1.5v cell in unmodified/non-adapted 1.3v mercury cell camera

I've always used the built-in light meters on my still cameras, and a handheld meter for my cine cameras. I had an adapter for my OM-1 that allowed me to use a 1.5v 386 cell without modification, but I've since had it modified and calibrated to use the 1.5v 625 cell directly. I've just received (today) a Canon QL17 GIII rangefinder camera. The adapter/386 didn't work. It may be a dead cell, or the adapter may have died. (I'll get another 386 cell at lunchtime.) For the present, I have a 625 cell in it.

 

If I continue to use the 625 cell, I'll need to compensate for the higher voltage. I'm pretty sure the factor is two stops; and I'm pretty sure that with ASA 400 film, a setting of ASA 200 on the camera is correct. Since I rely on accurate meters and don't have to think about compensation, I need a refresher. Is 'two stops' equal to 1/2 of the film ASA rating? If I am correct that a two stop compensation would be using ASA 400 film and setting ASA 200 on the camera, then is it true that if I use ASA 100 film I should set the camera's ASA to 50?

 

Or suppose I'm using a vintage camera with and a vintage light meter. If I want to compensate for the meter reading by two stops, would I go down two shutter speed increments from, say, 1/500 second to 1/250 second?

 

Obviously, if the over-volted meter is reading two stops high, I can simply set the aperture two stops lower than what it says. But am I correct that using a modern 1.5v cell in a camera or meter designed for the old 1.3v mercury cell reads two stops high?

ASA 400 to ASA 200 is one stop. ASA 400 to ASA 100 would be two stops. I also use a QL17 GIII as well as a Canonet 28. I use the CRIS camera M9 battery adapter in both and they work vey well. It allows you to use a 1.5 volt silver battery because it has a diode that reduces the voltage from 1.5 volts to 1.35 volts. I also use the adapter in my old Nikons and Nikkormats. They are not inexpensive but you only buy them once. I have tried most of all of the other solutions for the mercury battery problem and never found any that really worked very well.

My Canonet QL17 GIII works fine with the alkaline battery. The meter is reasonably accurate as is. However, if you find yours is off by 2 stops there is no easy compensation as i would expect the error would change as the battery run down.

You would have to test your camera to see how much off. I doubt that you would get 2 stops off.

That is the problem with alkaline batteries. As soon as you start using them their voltage starts to drop. Your meter will get less accurate as the voltage drops. The advantage to mercury batteries and silver batteries is that their voltage remains constant until they die. I have had silver batteries that have lasted 2 to 3 years and the meters were still accurate.

ASA 400 to ASA 200 is one stop. ASA 400 to ASA 100 would be two stops.

 

I must have misremembered.

 

I also use a QL17 GIII as well as a Canonet 28. I use the CRIS camera M9 battery adapter in both and they work vey well. It allows you to use a 1.5 volt silver battery because it has a diode that reduces the voltage from 1.5 volts to 1.35 volts. I also use the adapter in my old Nikons and Nikkormats. They are not inexpensive but you only buy them once. I have tried most of all of the other solutions for the mercury battery problem and never found any that really worked very well.

 

I do have an adapter that I bought a very long time ago. 'M9' sounds familiar. [i've just looked at the CRIS website, and I think that's where I got it.] I was buying a new Pelican-style case at Hardware Sales for my Olympus kit, and looked for a 386 battery there. They didn't have one, so I still don't know whether the battery is bad, or if the adapter failed.

If the CdS cell works like a resistor, in series with a meter and battery, then the exposure change should be linear with voltage.

 

It is known that some are up to two stops off, so they aren't so linear as one might expect.

 

Since I mostly use them with black and white film, with enough latitude, and with a quick comparison

to sunny-16, I usually find them close enough.

 

On the other hand, I have an FE2 that is two stops off with the right battery. You never know.

With my Minolta Hi-Matic 7s I tried both 1.3v and 1.5v and there was a one stop difference

 

My Petri FT SLR which I just tested is a half stop out in cloudy bright light. The 1.5v battery I'm using is new and reading 1.56v. The older 1.3v battery is reading 1.36v (I saved a number of 1.3v batteries from cameras I bought and none of those batteries were dead)

 

It seems different cameras will yield different results, as you can see from the two I just tested

I've just put a 1.5v alkaline cell (625A) in my QL17 and the needle is dead-centred in the blue -good- region when I press the battery check button. I also get a reading that agrees well with my DSLR, to less than half a stop.

 

I measured the cell voltage, and it says 1.504v on my DVM.

 

So, two stops out? I don't think so!

 

If the needle is anywhere in the blue region with the battery check button pressed, then you're good to go. That's what the battery check is there for.

 

Incidentally, the check button only works properly with the camera on a manual setting - for both aperture and shutter speed. If you put the camera into Auto exposure the needle position is influenced by light, regardless of whether the check button is pressed or not.

 

In any case the difference between 1.35 and 1.5 is barely 10%, and since a one stop change is a doubling or halving of exposure, a pitiful 10% change in light reading is comparatively nothing.

Edited May 8, 2019 by rodeo_joe|1

I've just put a 1.5v alkaline cell (625A) in my QL17 and the needle is dead-centred in the blue -good- region when I press the battery check button. I also get a reading that agrees well with my DSLR, to less than half a stop.

 

I measured the cell voltage, and it says 1.504v on my DVM.

 

So, two stops out? I don't think so!

 

If the needle is anywhere in the blue region with the battery check button pressed, then you're good to go. That's what the battery check is there for.

 

Incidentally, the check button only works properly with the camera on a manual setting - for both aperture and shutter speed. If you put the camera into Auto exposure the needle position is influenced by light, regardless of whether the check button is pressed or not.

 

In any case the difference between 1.35 and 1.5 is barely 10%, and since a one stop change is a doubling or halving of exposure, a pitiful 10% change in light reading is comparatively nothing.

 

I think if a camera is 2 stops off it will be 2 stops off no matter which battery you use. Although the Cds cell responds to light is linear but all of the metering circuit that use Cds cell tried to make it non linear. They tried to make it logarithmic but not very well. Modern meter with silicon cell used logarithmic amplifiers and their response are more accurate.

I don't actually know if the QL17 is two stops off. I'm making an assumption based on someone else's experience, and others' experiences are different.

 

I think what I'll do is take the FM3a, and a light meter along when I take the QL17 out. I can compare the QL17 to another camera and to the light meter, and adjust it accordingly.

I have 2 cameras that use the 625 cell. The Olympus 35RC with the alkaline battery the meter reads high about 1 to 1 and 1/2 stops. The Canonet QL17 GIII which reads about 1/3 stop high.

Some camera designers seem to have foreseen the difficulties with batteries and used bridge circuits to 'immunize' their cameras:

 

The trouble with mercury batteries (and what to do) (scroll down to 'bridge')

 

My beloved cameras from the Workers' and Peasants' State were among these:

I also have 2 Canon EF (the old ones that use FD lenses) and they use 2 625 cells. I found that using alkaline batteries in them doesn't affect the meter accuracy at all.

The EF uses 1.5 just fine as it's designed that way. My other Canons are off by at least a stop with 1.5s. First time I put in a 1.5 in my F1, not knowing the change, I said to myself, "WTF".

The other day, I bought the Pocket Light Meter app for my iPhone. Today I put a 1.5v #625 into my Asahi Pentax clip-on light meter. I aimed the iPhone out the window, and the Pocket Light Meter said that I should use f/5.0 at 1/250 second. I aimed the clip-on meter out the window, and set the shutter speed to 1/250 second. With the meter switched to 'H', the needle is at the edge of the black marking. That is, the needle is halfway between f/4 and f/5.6. I assumed ASA 400 film, and set the meter's ASA dial to 200. With this initial test, it looks like I might be able to use the meter with a 1.5v cell by reducing the ASA setting from 400 to 200. It's going to be a while before I'll have a chance to get out the Pentax SV and try it, after more comparison readings between the iPhone and the clip-on meter, with film. When I get a chance, I'll compare the Pocket Light Meter to the QL17 to see if I can 'calibrate' the meter with the ASA setting on it.