Virtual Bulb mode with script ? - Script Writing - CHDK Forum
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Virtual Bulb mode with script ?

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Offline rvk

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Virtual Bulb mode with script ?
« on: 17 / October / 2012, 15:47:09 »
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My G1X (with chdk version 1.2.0-2213) does not have Bulb mode, which is something I really would like to have. After trying out the "shutter speed override" feature, I got this idea :

A script that 1) set shutter speed override to 2048, 2) start exposure on first press of shutter button, 3) listen for next press of shutter button during current exposure which should 4) interrupt current exposure and then repeat from start.

It would be a Bulb toggle rather than a classic bulb, but that is even better.
Would it be possible to do this with a script ? Any design ideas are welcome.
   
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Offline marsrover

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Re: Virtual Bulb mode with script ?
« Reply #1 on: 23 / October / 2012, 14:01:08 »
I am also interested in a script such as this one. However I can think of a few hardware limitations that would prevent this.

1, a while ago someone helped me with a script that would flash the AF light after taking a long picture (to help my timing with light painting) The issue with this script was it would flash after the dark frame subtraction had done it's business and after the file was written. (so it was twice what the shutter speed was, plus a bit extra to write, before it would flash) Which leads me to.

2. This means the camera can only do one thing while taking a picture, and that is take a picture. I don't think a script can be running in the background at the same time.

If I'm wrong, (which I hope I am) then I would adore a script such as this.
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Offline reyalp

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Re: Virtual Bulb mode with script ?
« Reply #2 on: 23 / October / 2012, 16:56:10 »
Quote from: marsrover on 23 / October / 2012, 14:01:08
2. This means the camera can only do one thing while taking a picture, and that is take a picture. I don't think a script can be running in the background at the same time.
This isn't true. If you use shoot(), then it will block until the shot is (mostly) done but if you use key presses like press("shoot_half") etc, then the script will run during the shooting process. However getting back to the original question, there is no way for script to block the shooting process during the exposure. This might be doable in theory, but it would require reverse engineering more of the Canon shooting process. If you are handy with ARM disassembly, some people here may be able to give you ideas for starting points.

You can control the mechanical shutter using eventprocs (if you use a "native call" enabled build http://chdk.wikia.com/wiki/Lua/Lua_Reference/Native_Function_Calls ) but that doesn't really help, because most of the shooting process is in software. You could start say a 10 minute exposure, and manually open close the mechanical shutter at arbitrary points, but you'd still have to wait for the full 10 minutes and get all the noise etc associated with a 10 minute exposure.
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Offline rvk

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Re: Virtual Bulb mode with script ?
« Reply #3 on: 24 / October / 2012, 10:48:17 »
Ok, I guessed it would probably be too good to be possible but you never know.
Thanks for the input.

@marsrover : Could you please share the AF light flashing script you mentioned ? I'm also doing lightpainting, and the G1X does not add dark frame subtraction so I suppose it would work great.

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