M6 meter bad on low batteries?

ericdan · Oct 2, 2014

Hi, just shot two rolls of tri-x this week with my usual metering technique. Never had a consistent problem with underexposure.
This week 80% of my two rolls were heavily underexposed. I assume the few good ones were accidental over exposures.
Then I noticed my battery died. Could that have caused the problem?
I was under the impression that the meter reads correctly until batteries die. Does accuracy diminish as batteries are close to the end of their lifetime?

If that's the case is there any way to tell when to change the batteries other than when the red arrows go?

MattKing · Oct 3, 2014

What type of batteries were you using (size and type)?

Alkaline batteries are not consistent over time.

summicron1 · Oct 3, 2014

to answer your question
: Yes.

Always keep an eye on exposures and when the meter says something weird, considering it lying scum and use what your brain tells you.

And keep fresh batteries handy. Even if they don't show as bad with whatever battery test function your camera has, they can be off.

Michael W · Oct 3, 2014

In my experience, when the batteries in the M6 were dying the meter recommended over-exposure. That was silver oxide.

ericdan · Oct 3, 2014

They were either SR44 or LR44. I don't remember now.

Xmas · Oct 3, 2014

Only 2xsilver or lithium in user handbook from memory check handbook before you buy more...

Truzi · Oct 3, 2014

My brain tells me to use a light meter.

Yes, some batteries' output lowers as they drain/age, and if the circuit is dependent on a certain voltage or current, this can throw things off. Using an actually voltmeter is better than relying on any device's built-in warning. However, using a meter is not foolproof either.

It's best to choose a type of battery that does maintain a certain spec as is wears. Some types are better at giving a constant output until they are spent, while others have a long and steady decline in output.
Also make a point to change batteries at regular intervals (they are not expensive, all things considered). Figuring out that interval is the hard part.

gone · Oct 3, 2014

A multi meter is your friend. I have one that I bought from Harbor Freight about 5 years ago for $4 and it's still going strong. I find it indispensable w/ camera batteries, because there's often a huge difference in how some meters work between say 1.44 volts and 1.36 volts.

Xmas · Oct 3, 2014

The silver cells drop their on load voltage so rapidly that the red lights go out before the voltage goes down much. Their internal resistance goes up near to end of life.

The M6 was quite high current when on or at least mine was so a battery test button was not really necessary.

More modern batteries may have more current capacity so that might compromise the mechanism.

New batteries only lasted a week end in mine cause I left the camera on.

Chan Tran · Oct 3, 2014

I don't know specifically about the M6. Mostly older meter design the meter is not correct when the battery is low. Newer design doesn't have this problem.

benjiboy · Oct 4, 2014

I should have thought that a camera of this quality would have a Wheatstone bridge circuit http://esg.mit.edu/videos/circuits-...stone-bridge-what-it-does-and-why-it-matters/ in it's metering circuits so that as the battery runs down it doesn't give progressively more inaccurate exposures as it runs down , if it can't reach the correct voltage it drops dead.

M6 meter bad on low batteries?

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