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Wednesday, 19 February 2014

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Here’s a theoretical question for you Ctein: it is a known fact that cold weather depletes a battery (though I’m not sure if it’s limited to Li-ion batteries or is a general phenomenon across types of batteries). Would there be some benefit to siphoning off some of the battery’s output into a small heating mechanism that could, theoretically, keep the battery warmed to some temperature that would negate this loss of charge? Running the math on this is frankly beyond me, and I can’t imagine I’m the first person to guess at something like this, but the idea does intrigue me, so I thought I’d propose the question to you.

Good grief, temps in °C! & this from a USA source. Thanks Ctein. Now all we need to do is fix up the US fluid ounces/cups/gallons fiasco. &, better still, while we're at it convert the USA to metric.

A friend took a external battery pack that he kept under his coat with the lead exposed to the camera; worked faultlessly and they were working further north at the temperature -40 F and C.

I think the battery is a big issue for these smaller camera systems. If I'm shooting a full day event on my Nikon dslrs I'll shoot maybe 2000-3000 frames all without having to swap out the battery. I'd love to go M4/3 but the idea of having to change the battery 7 or 8 times on a job is just too much....

"Luckily, I was in Minneapolis in the latter part of January..."

Now those are words I never thought I'd see together...

Looking forward to the photos!

I'm curious as to why low temperatures would affect image noise. Is it because noise is caused by heating of the sensor, and you were hoping the cold ambient temperature would counter that?

And BTW, I'm with Ian Macdonald. Dear U.S.ers; please catch up with the rest of the world and go metric! And while you're at it, update your credit card processing. Whenever I pull out a credit card in the U.S. I feel like I've stepped back in time 15 years!

Norwegian photographer Morten Hvaal shared a photo on facebook today that reminds me of your tests: https://www.facebook.com/photo.php?fbid=10152076515017911&set=a.405944522910.188885.206416557910&type=1&relevant_count=1

So, conlusion: Chill man, cameras can handle a chill?

The decrease in battery capacity with falling temperature is generic to all batteries. However, the magnitude of the effect depends on the chemistry of the battery. Going solely on memory, I think lead-acid batteries fare the worst while lithium based chemistry is the best. I know lithium primary cells are used for high-altitude balloon research where they may wind up getting cold-soaked at minus 70 F. NiCd and NiMH rechargeables are somewhere in between; those are the ones that usually wind up in the packs designed to go under clothing.

hi Ctein, look forward to seeing your pictures! Here in Ontario I go out every weekend sometimes in -28C or lower to take pictures, using my Olympus EM5 and my Fuji XE1 with no problems whatsoever. If there is constant blowing snow I use plastic-wrap over my Fuji. I carry spare batteries for both, but as I stop at about the 3-hr mark, haven't had to use them. The important equipment is the clothing, hand-warmers and toe-warmers are what I think about, not the cameras. The lesson is in the willingness to test and prep. Have a good trip!

Dear Ed,

All systems are subject to thermal noise. Random atomic motion (a.k.a. “heat”) occasionally kicks an electron up into an excited state. It's no different from an electron that's been kicked there by a photon hitting your film or sensor. The lower the temperature, the less this occurs.

The thing is, in a digital imaging system, there are many different sources of image noise. If the non-thermal sources are larger, then dropping the temperature won't make much of a difference in the amount of noise in your photographs. But, many scientific imaging systems use cooled sensors to reduce the noise level; they are designed to be extremely low-noise systems to begin with, so thermal noise may be the greatest limiting factor, aside from statistical noise in photon counting.

The reason, by the way, that you don't see significant thermal fogging of film is because it takes 2-4 excitations in the same silver halide crystal within a short period of time to produce a stable latent image. Thermal excitation is infrequent enough at normal temperatures that that coincidence doesn't happen very often. That's why film can go for years and years before it develops a significant level of fog.

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Dear Ben,

You reminded me to remind people–– a very important part of your cold weather kit is zip lock bags. You need something to put your camera in that's airtight before you bring it back indoors, or the same thing is going to happen to it that happens to that jar that you take out of the freezer and sit on the counter.

If you can't wait hours to look at your photographs, remember to pop out the memory card while the camera is still outdoors and slip it in your pocket. Its thermal mass is so low that you don't have to worry about condensation or frost when you bring it indoors.


pax \ Ctein
[ Please excuse any word-salad. MacSpeech in training! ]
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I understand temperatures reported in Celsius. In fact, these days I give my age in Celsius as well.

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