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Lowest power CHDK cam?

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Offline albo

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Lowest power CHDK cam?
« on: 21 / August / 2010, 12:18:45 »
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Hi Folks,

I'm looking into using CHDK-equipped canon point-and-shoots for remote deployment in tropical forests as sensors.  So, I'm interested to see if anyone knows which chdk-supported canon models have the lowest power consumption?  They would be sitting there with screens off, waiting for motion triggers most of the time, and occassionally taking pictures.

Just to be clear, I'm not interested in battery life per-se, but rather the actual power consumption of the camera (since i'll probably have it connected to a solar cell, etc.)

thanks for any thoughts!

allie

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Offline fudgey

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Re: Lowest power CHDK cam?
« Reply #1 on: 21 / August / 2010, 16:05:03 »
A rather interesting question. You could probably calculate this from Canon's marketing data (compare their battery life shot count specification to battery capacity in Wh) to get an idea. The results may be a bit crooked in favour of simpler cameras if the tests heavily use of battery drawing features such as the LCD, super-zoom lenses and manual focus.

There probably aren't huge differences in your use, but some factors that may somewhat reduce power consumption (other than the LCD) over other models are
- newest Digic version is probably more power efficient for the same task (assuming heavier noise reduction etc. doesn't tip this the other way around).
- sensor with fewer pixels probably consumes less power and its RAW images will require less signal processing power.
- lack of iris (no Av mode) could save some power (I'm guessing an ND filter is lighter and it probably doesn't need to be swung as often as the iris).
- cameras with higher minimum input voltage specification (lithium or 4xAA battery instead of 2xAA) could be more power efficient.

My gut feeling is that the cheapest Digic IV camera with a lithium battery -- whatever that is -- could be a good candidate.

Note that you'll have to use external motion triggers instead of CHDK motion detector if you want serious power savings from disabling the LCD (most of the power savings of display off actually comes from disabling the sensor and related things, not the LCD => no sensor means no live view => no image for motion detection to work on). The LCD can be disabled without shutting down the sensor at least on cameras that have a video output jack (are there any without one?), but that enables the video driver which in turn requires some power (not much but enough to annoy). LCD backlight can be powered off on any camera but that doesn't help a much in comparison. Also remember that idling in manual focus mode requires more power than autofocus.
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Offline albo

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Re: Lowest power CHDK cam?
« Reply #2 on: 22 / August / 2010, 23:17:56 »
thanks for the reply, fudgey.  So, a question about the motion detection: are you saying that i don't save much power by turning off the lcd (either via chdk, or a video out plug)?  The sensor and related chips are what are actually sucking power, and not the lit-up LCD itself?

Anyway, you've given me some good things to look into.

thanks,
allie
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Offline reyalp

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Re: Lowest power CHDK cam?
« Reply #3 on: 23 / August / 2010, 00:25:28 »
Quote from: albo on 22 / August / 2010, 23:17:56
thanks for the reply, fudgey.  So, a question about the motion detection: are you saying that i don't save much power by turning off the lcd (either via chdk, or a video out plug)?  The sensor and related chips are what are actually sucking power, and not the lit-up LCD itself?
Correct. Turning off the back light will get you a little bit, but not much.

This thread may be useful: http://chdk.setepontos.com/index.php/topic,3872.0.html
or go direct to the main conclusions from that thread at http://bugsplatter.id.au/chdk/a590-power-2.html

I wouldn't expect huge differences in power draw between models, if they are all sitting and idling in MD.

Some other measurements can be found at http://chdk.wikia.com/wiki/Camera_Power_Consumption
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Offline fudgey

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Re: Lowest power CHDK cam?
« Reply #4 on: 23 / August / 2010, 02:03:01 »
Also note that half shoot (MDFB fast react mode) draws somewhat more current than normal idle (MFDB slow react mode) because things like the aperture and focus mechanics are being held at their final positions. This difference is not as huge as it is between rec and play modes or rec mode with LCD+sensor enabled/disabled.
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