deep-sea autonomous shooting - page 2 - Script Writing - CHDK Forum
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deep-sea autonomous shooting

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Offline glowgoose

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Re: deep-sea autonomous shooting
« Reply #10 on: 12 / November / 2009, 01:15:28 »
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Here is another deep-sea scenario for you:

suppose I want to shoot a giant squid or something of that sort. I have my camera hanging in the water (deep, totally dark) looking at a luminescent lure 2 meters in front of it. The lure is basically 1/3 of a green glowstick. Can I program my camera to respond with a series of wide-angle shots when the glowstick abruptly disappears from view? (lets suppose for now that lighting is not a problem - for example, let's assume we can use the signal that camera tries to send to the flash to turn on an LED bank) I guess it comes down to the question whether the motion detection of the camera is good enough to detect disappearance, or a rapid jerk, of a speck of weak light (on a completely black background) in the middle of its field of view.
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Offline reyalp

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Re: deep-sea autonomous shooting
« Reply #11 on: 12 / November / 2009, 01:48:54 »
The only way to figure that out is testing. Motion detection uses the live viewport (the same thing you'd see in the LCD screen, roughly). In general, motion detection suffers in dark conditions, because the more you crank up the ISO the more noise there is, and noise looks just like motion. Motion detection should be fine detecting a light being blocked out or moved against a dark background, but the limits will have to be determined by experiment. As long as your light is significantly above the noise floor, it should be OK.

You should be able to set up a decent test without actually taking it on a dive. Use the same luminosity lure in a dark room at the same distance and test different motion detection settings.

Most of the A series will probably fit the "slightly smaller than G9" requirement. The SX200 might be another option.

This advice of testing applies to anything you plan to use CHDK for. Unless someone happens to have used the same camera in very similar circumstances, the only way you are going to get a reliable answer is controlled testing. If you are serious about using CHDK, you are going to have to need hands on experience with the scripting system anyway, so the sooner you start trying to actually do things with it (even if they are very simple low fidelity tests) the better off you will be. Remember that CHDK is a hack. Most behavior is not well specified, and the only way to really know how something will work is to try to do it.

fbonomi mentioned covering up the flash. I'm pretty sure that some flashes can be damaged by doing this, but I may be wrong.
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Offline mattkime

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Re: deep-sea autonomous shooting
« Reply #12 on: 13 / November / 2009, 10:13:55 »
i've done a fair amount of work on time lapse of this scale. i have a script which i would recommend using to take a pic every 5-15 minutes. However, it is my experience that programmatic image capture is subject to very small yet very important instability. This seems to happen somewhere in the range of 1 in 100 to 1000 shots. My solution has been to have the camera shut down on error. Not ideal but better than nothing.

I've used an arduino microcontroller to keep the camera on. It examines the amount of power flowing to the camera and if it drops to zero then the arduino "presses" the power button. This does require some camera modding which looks awful at first but if i can do it, so can you. Its possible that this could also determine when the camera is taking a pic (due to increased power usage) and fire the flash at the correct time. While the arduino might look like unnecessary complication and therefore a point of failure, its my experience that its extremely stable.

Eye-fi would be great for getting the pics from the camera but i'm skeptical that you'd have wifi down there.
« Last Edit: 13 / November / 2009, 10:26:31 by mattkime »
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