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Continuous shots in Motion Detection mode

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Continuous shots in Motion Detection mode
« on: 12 / May / 2008, 05:28:46 »
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Hi guys,

I found CHDK a few days ago and I have to first say I'm impressed  :) . I've installed the latest AllBest build on my SD700 and it seems to work well. I have been playing around with some scripts including OMNI-invalometer. However, I'm quite interested in using a Motion Detection script to capture lightning.

I tried to help myself by searching for scripts, but now I'm a little stuck. As far as I understand things, some motion detection scripts are quick enough to capture the up-bolt of the lightning strike which triggers the camera to take a picture. I tried "Adaptive MD.bas" and "Motion Detection.bas", but I couldn't quite get them to work fast enough. I stumbled across "MD Lightning7.bas" tho, which appears promising. It seems to work quickly, which is a good start.

My understanding of lightning shots is that one would need to take multiple shots quickly after the up-bolt to ensure you get the "perfect" shot of the lightning bolt. This said, I don't see a way to put the camera into continuous hi-speed drive while still in motion detection mode. Could anyone advise me how I could do this?

Cheers,
SuperSized

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Offline vine

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Re: Continuous shots in Motion Detection mode
« Reply #1 on: 12 / May / 2008, 05:35:47 »
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Re: Continuous shots in Motion Detection mode
« Reply #2 on: 12 / May / 2008, 06:18:14 »
Great, thanks vine and congrats to Fudgey for this great code.   :D

Is there any way of making the continuous drive quicker? As it stands I doubt I would get more than 1 picture of the lightning.

Sorry for the noob questions

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Offline vine

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Re: Continuous shots in Motion Detection mode
« Reply #3 on: 12 / May / 2008, 06:21:10 »
there is nothing faster than using the cameras built-in burst mode (which is what fudgeys script is using)
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Re: Continuous shots in Motion Detection mode
« Reply #4 on: 12 / May / 2008, 06:35:40 »
Cheers, thanks. Since lightning is dynamic (i.e. has motion), do you think if Fudgey's MD script was set to single pics and optimized for speed (according to his post), that the camera would be able to rattle off a few shots of lightning? Or am I going to have to try this myself?  :P

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Offline vine

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Re: Continuous shots in Motion Detection mode
« Reply #5 on: 12 / May / 2008, 06:45:31 »
When set to single pics it will take one pic per strike.
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Offline mx3

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Re: Continuous shots in Motion Detection mode
« Reply #6 on: 12 / May / 2008, 06:57:33 »
My understanding of lightning shots is that one would need to take multiple shots quickly after the up-bolt to ensure you get the "perfect" shot of the lightning bolt.
the problem is your camera is powershot digital camera.
it is not special cam which can make shoots every 10(50) msecs....

botleneck is:
- amount of RAM available
- time required to make shoot
- time to be ready to make next shoot
- SD card write speed

I did no measurements to check what is minimal interval between shoots is but I'm sure you can make only one shoot of the same lightning bolt.

to make several shoots without storing them to SD card camera must have either alot of RAM available or very quick writing speed to memory storage device (SD card)


so.
You cant make several shoots of the same bolt.
I would be happy if i'm wrong


This said, I don't see a way to put the camera into continuous hi-speed drive while still in motion detection mode. Could anyone advise me how I could do this?
motion detection feature do not depend on mode you have selected.
You can make any count of shoots as you like (using either CHDK or original fetures).

I'm not a photographer.


I would suggest you to make several shoots in most quick mode (no lightning).

analising exif data you could calculate time difference between shoots.
if it is small enough to capture the same bolt twice - good for you ( but I don't beleive it)
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Offline vine

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Re: Continuous shots in Motion Detection mode
« Reply #7 on: 12 / May / 2008, 07:15:49 »
A single lightning bolt consists of about five primary discharges about 0.05 seconds apart. Lightning strikes with up to twenty primary discharges have been observed. So I think it is possible to take more than one picture of the same strike as long as you can keep exposure times low. If you think RAM or card write speed might be limiting (but most likely they won't for bursts of 5 or less photos) you can reduce photo resolution to achieve smaller file sizes.
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Re: Continuous shots in Motion Detection mode
« Reply #8 on: 12 / May / 2008, 08:01:48 »
Thanks for all the useful ideas guys. I'll try putting some of them into practise the next time a thunderstorm rolls by ...  :)

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Offline Pauls9

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Re: Continuous shots in Motion Detection mode
« Reply #9 on: 12 / May / 2008, 09:56:33 »
Or I guess you could use a slightly longer exposure and have several discharges superimposed...?

 

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