Exposure metering batteries.

[John King]

There has been a lot of talk about the voltage difference of the Mercury 1.35V and the Silver Oxide/Lithium 1.5v used in cameras. For the 1st time over this last weekend I did a test where I used my Minolta SRT101b and my Minolta XE1. They should have 1.35v and 1.5v batteries respectively. The images were quite a mix with some bland subject and others with high contrast.

I used the 1st 11 exposures of a 24Exp Fuji Superia film in the SRT101b, rewound the film and reloaded it into the XE1 and winding it forward and missing out the 12th frame and finished the film off. After processing the density level of every frame was precisely the same. I confirmed this by making a proof sheet and the exposures were all within quite a tight tollerance. Not even colour balance changes were evident.

I wonder if the talk about the difference in voltage has been exagerated?

[MikeHeller]

I recently read an article I found on the internet (can't remember where but was googling the difference between these batteries for an exposure meter). As far as I can make out the two issues (other than cell size) are:
a) The consistency of voltage delivered with time (age of battery) which can be a problem with non silver batteries.
b) The higher voltage of the silver batteries which may give a slightly different exposure value from the discontinued mercury cells.
Mike

[Svend]

Interesting finding, John. I have been puzzling over the same question, having an old Gossen Lunasix 3 meter still with the original Hg batteries. I heard that #675 hearing aid batteries are the right voltage, but being zinc-air type they're apparently rather short-lived. I might try them anyway to see how they work -- cheap experiment, as they're only about C$1.50 each. I will also try the silver oxide SR44, which are higher voltage, but I really would like to see if it makes any difference in the readings. I will compare to a known good meter at various light levels and see what I get. From your tests, maybe the Gossen will be fine...? Every meter is wired differently, I suppose, so perhaps I won't be as lucky.

Mike, I wonder if a meter like the Gossen can simply be re-calibrated using the Zero-adjust to compensate? And if the voltage shift means a linear error response across various light levels? I will check that out....

Thanks for posting. Reminded me that I need to try this soon as I have some night photography coming up that I need the Gossen for.

Svend

[M Stewart]

Originally Posted by John King

There has been a lot of talk about the voltage difference of the Mercury 1.35V and the Silver Oxide/Lithium 1.5v used in cameras. For the 1st time over this last weekend I did a test where I used my Minolta SRT101b and my Minolta XE1. They should have 1.35v and 1.5v batteries respectively. The images were quite a mix with some bland subject and others with high contrast.
... ...
I wonder if the talk about the difference in voltage has been exagerated?

Which battery did you use for your tests?
I've got my first interchangeable lens SLR, an SRT101, on a shelf which might benefit from an outing.

[John King]

I have just checked and the battery fitted at the moment and it is a Silver Oxide PX 625 Energiser.

The on/off switch - that stupid almost recessed disc thing in the base has a battery check included and on mine when it is turned to 'BC' the needle is resting almost dead centre which is close enough for me.

[M Stewart]

John, many thanks.
My SRT101 was very reliable until it went through an airport Xray scanner, or three, back in the 1970s. After that it was still reliable, but I found that my 'chrome exposures needed a 1/3stop film speed adjustment. (e.g. 64ASA to 80ASA)

[John King]

I wasn't aware there were X Ray scanners back in the 70's

[JOReynolds]

The indicator in a typical CdS follow-the-needle meter is a simple d'Arsonval voltmeter, in which a needle is attached to a coil that moves within a magnetic field. The change between a 1.35V and a 1.5V will probably be around half a stop.
I agree with John King - the discrepancy can be ignored.

[alexmuir]

There is a battery sold for hearing aids which is 1.4V. You get a pack of 6 or 8 for about £3.50. I think they are alkaline, and the code is 675. They are larger than the size 13, or 312. They are a reasonable fit in some cameras that used the 1.35V mercury cells. If the 1.5V types don't cause a significant metering difference, they would be preferable as they tend to last a lot longer. I use two 675s taped together in my Nikkorex 8F cine camera.
Alex


Sent from my iPhone using Tapatalk

[Svend]

Alex, a quick tip that I learned to make the smaller-diameter 675 hearing aid batteries fit into a larger compartment, is to use a little rubber grommet around the perimeter of the battery. This works great for single batteries. But for doubles, I do as you do and wrap them in a few turns of electrician's tape to take up the gap. Grommets should be available at any auto parts store.