Has anyone used CHDK for high speed shots of bullets ?

KScott_NZ

3

« on: 13 / June / 2009, 21:21:52 »

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Just curious, has anyone used the high shutter speeds with motion detection for bullets or guns in action ?

I've done a search on the forum for "bullets" but nothing came up.

Been hanging around the forum for ages and toying with the idea of seeing what high shutter speeds would capture in action, as well as air rifles (which shoot a lot slower than power burners). Currently I'm on the lookout for a 2nd hand camera to use CHDK for high shutter speed shots (with a lot of light added !).

Cheers.

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mikeage

19

Re: Has anyone used CHDK for high speed shots of bullets ?

« Reply #1 on: 14 / June / 2009, 00:00:21 »

What's the advantage (besides ease of setup?) between a high speed shutter (with all sorts of triggering delays) over a long shutter with a high speed flash?

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reyalp

14119

Re: Has anyone used CHDK for high speed shots of bullets ?

« Reply #2 on: 14 / June / 2009, 01:02:22 »

I've toyed with this idea a bit. If the more optimistic estimates of shutter speed are correct, it should be possible to nearly stop bullets in flight, but MD isn't even close to fast enough. 1000 feet/sec is pretty modest for a bullet, yet MD takes several tens of ms at best. Triggering with MD and catching the round 50' down range doesn't leave you with much of an interesting shot. A small, fast object like a bullet is also about the worst case for MD, and the exact latency may vary by tens of ms.

So you need something else to trigger the exposure. You can do this by tying something (like a hacked up chronograph) into the USB remote, but as mikeage says, you need to deal with various latencies, they may not be predictable down to the time scales you need. Using a flash instead would make this simpler, but might not be viable in your shooting environment.

You could probably get some pretty neat impact effect shots (i.e. shooting soda cans or melons) with regular MD.

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Don't forget what the H stands for.

KScott_NZ

3

Re: Has anyone used CHDK for high speed shots of bullets ?

« Reply #3 on: 14 / June / 2009, 17:28:05 »

Many thanks for the suggestions.

Luckily air pistols and rifles shoot at a much lower speed (500-> 900 feet per second on average) vs a powder burner rifle (1800 fps).

Stumbled across this article
http://www.diyphotography.net/diy_high_speed_photography_at_home
which reinforces suggestions here of an open shutter and using a fast flash.

I was thinking of motion detection for air pistol into the target (500 feet per sec max).

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fudgey

1705
a570is

Re: Has anyone used CHDK for high speed shots of bullets ?

« Reply #4 on: 15 / June / 2009, 15:22:43 »

Quote from: KScott_NZ on 14 / June / 2009, 17:28:05

I was thinking of motion detection for air pistol into the target (500 feet per sec max).

CHDK MD is nowhere near fast enough. Optimized CHDK MD (not available in all ports because it requires someone with that camera to implement it) reacts in roughly 40 to 100 ms depending on camera and luck (there's significant variance). Unoptimized is sometimes equally fast, sometimes beyond 200 ms.

Even in 10 ms (0,01 s) your bullet will travel 5 feet, and that 10 ms if far beyond MD react time and even way beyond its repeatability. You'll get much better results using synced mode USB remote pre-triggered from your gun's trigger by some cunning mechanical arrangement. Even then you'll probably have too much variance to catch every bullet, but it might actually work, unlike MD (unless you do what reyalp mentioned and try to get pics of something breaking from the impact).

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KScott_NZ

3

Re: Has anyone used CHDK for high speed shots of bullets ?

« Reply #5 on: 15 / June / 2009, 16:30:13 »

Thanks for the advice. Spent last night scouring the interweb looking at sound activated camera/flash triggers, so may go down that path. But the CHDK will help in getting higher than usual shutter speeds.

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headless_rabbit

4

Re: Has anyone used CHDK for high speed shots of bullets ?

« Reply #6 on: 17 / June / 2009, 01:50:57 »

I don't have results yet, but I am currently working on a DIY high speed flash system (LED array connected to a picaxe microcontroller) for catching high speed stuff. (falling ink blobs)

using a microphone seems like a good way to catch the sound and trigger a quick LED flash, but building a circuit to catch that sound is currently beyond my skills, so i'm just making an box filled with LEDs that flashes quickly, and shooting against a very matte black backdrop. when the bullet is in the frame, one of the light flashes will (hopefully) catch it, letting you see the object clearly. if it flashes too fast, you will see multiple ghost like copied of the object moving across the frame. the black backdrop absorbs excess light from the flashes that pick up nothing.

if you aren't a DIY guy, but want a similar effect, cheep LED Christmas lights flicker at 60hz. you might have luck capturing pellets or paint ball bullets at this speed. its an ugly solution, the results may not be the best, but its a cheep and easy way to 'try out' an idea before investing a lot of cash into a proper system.

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