Time lapse on A480? - General Help and Assistance on using CHDK stable releases - CHDK Forum

Time lapse on A480?

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Time lapse on A480?
« on: 07 / September / 2010, 18:51:36 »
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Has anyone tried doing time lapse with a Canon A480? I've tried various CHDK intervalometer scripts with interval set to one second, but the camera shoots closer to a 10-second interval.

Guessing that the camera can't keep up with processing required at this rate I've tried to help it by setting color to "Black and White" (which I understand takes about one-third the memory of color); the image to a small "S" size (only 300K pixels); the compression to "Normal". But there is no change in the speed. (I also tried to lock the aperture and focus but this resulted in only one picture getting taken before the program stopped.)

If the camera can shoot video at 30 frames per second why can't it shoot these still images at one frame per second? Even if the buffer were filling up I would expect to get some pictures at a one-second interval before things bogged down.

I expect the camera is doing things I don't know about between images, but don't know what.

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Offline reyalp

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Re: Time lapse on A480?
« Reply #1 on: 08 / September / 2010, 00:52:09 »
Has anyone tried doing time lapse with a Canon A480? I've tried various CHDK intervalometer scripts with interval set to one second, but the camera shoots closer to a 10-second interval.
If it's actually taking 10 seconds, something is wrong. In general, an intervalometer should be able to come close to whatever the continuous rate given in the canon spec is (0.8 fps for a480). You should not expect to exceed this by much.

If you are saving raw or DNG, that can take several seconds by itself.

If you shoot long exposures (usually >3sec) the actual exposure time will be doubled because the camera does a dark frame as well.
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Guessing that the camera can't keep up with processing required at this rate I've tried to help it by setting color to "Black and White" (which I understand takes about one-third the memory of color); the image to a small "S" size (only 300K pixels); the compression to "Normal".
This kinds of settings don't tend to help shooting rate, because the camera still reads out the sensor at full resolution (you can verify this by taking a RAW image with the resolution turned down... the RAW will still be full size. edit: meaning the entire thing will have data, not just the file size) In some cases these modes are actually slower than full resolution because they require more processing.

The only thing that reduces the actual resolution of stills is using high ISO mode/low light modes found on some cameras. These do some kind of binning or down-sampling very early in the process, and tend to be much faster than other still shooting modes.
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If the camera can shoot video at 30 frames per second why can't it shoot these still images at one frame per second? Even if the buffer were filling up I would expect to get some pictures at a one-second interval before things bogged down.
Because the sensor has a dedicated readout mode for video, which actually reads out 640x480 instead of taking a full resolution raw and down-sampling it. It's not clear why Canon doesn't use this mode for 640x480 stills, but they don't.
Don't forget what the H stands for.

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Offline fe50

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Re: Time lapse on A480?
« Reply #2 on: 08 / September / 2010, 01:00:55 »
@bobcameron
You may try this intervalometer script (as reyalP stated, disable RAW): fast_shooter

 

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