Light Painting

bAjA's picture

Anybody got any ideas on where to start, if I wanted to use qc to make something like this: http://vimeo.com/5966947

My only thought would be to play with feedback type stuff, but i guess its not that simple...

cheers - bAJA

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cybero's picture
Re: Light Painting

Feedback, Interaction, Hand gesture - see Splatter Paint by dust

& paint by memo & Sweeping Body Movement post. CV Tools, Hough Lines also comes immediately to mind, as does Optical Flow Downloader [Developer's Tool example]

dust's picture
Re: Light Painting

light painting is more of an in camera effect pioneered by pablo picaso over a hundred years ago. its recent popularity spawned various advertisements such as a sprint campaign. this technique is commonly referred to as "light writing" and has been made popular again by the graffiti community running around town writing there names with led lights while they film.

this crew of light painters i guess they are calling it have an interesting show. there website says they are are using custom video effect software to light paint. this undoubtedly is true as i do not deny they didn't make some stop motion software but light writing is an in camera effect where as you open up the exposure of the camera.

its very common if you have ever messed with the settings of your camera or took a picture at a festival where someone is playing with glow sticks or something.

so doing this qc wouldn't be that difficult by opening your camera exposure up by like 15 seconds or something and queuing up a bunch of frames then using an interpolator to iterate through those frames.

recently i took a graduate class in visual perceptions and have been studying the visual phenomenon that that tricks your brain into making this effect possible. the phenomenon is called persistence of vision. where an after image stays on your retina for a few seconds. it is thought that iconic memory is the cause of short term vision memory.

if you want to experiment graphically with this type of phenomenological stimuli and not mess with a camera then i suggest checking out my illusion thread.

http://kineme.net/composition/dust/illusion

there is my illusion and some others posted. in particular the lilac chaser or phi phenomenon is a classic example of of how light writing works. actually there is a whole community of doctors and professors that study these things so there is more than than enough info on the net to get you started.

bAjA's picture
Re: Light Painting

@dust - cheers for the input on doing this with a stills cameras, but it looks to me like they are doing this with a live feed from a video source. Not just playing back a stop motion of pre-taken stills. I know you can get these kind of effects with low shutter speed on a video camera, but it seams to have a more interesting quality than just that.

@cybero - thanks for the links i will checkout the feedback used in these comps.

The more i think about it, the more it seams the effect i'm looking for may be as simple as camera into feedback patch, with the right balance of ambient light, camera exposure and feedback level.

At the moment its a possible idea for a production, so i'm considering the practicalities, but maybe I will find the time to build some test comps soon.

cheers -bAJA

laserpilot's picture
Re: Light Painting

Heres a light painting effect I made in jitter: http://vimeo.com/2374085

The trick was not just putting the feedback loop on everything but rather restricting the loop to a very small luminance range (ie the brightest pixel seen by the camera)..this allowed you to do it in places that weren't dark rooms..and it also allowed you to create a 'drawing layer' that you could use simple frame diff. motion detection to interact with

I've wanted to recreate it in quartz as it would be a lot faster, but would need more core image coding skills..that said, if you want my light painting patch for jitter I can post it

dust's picture
Re: Light Painting

yes please post a jitter patch. here is a basic example of one of the ways you could emulate an open exposure. just a simple feedback accumulation chain. you can adjust the after image life and feedback level to get various results on how long the streaks will stay on the screen. i suggest using this as a base then thresholding and blurring out feedback image then use that as mask layer to the original image. as it is now the effect is only applied to the overall image. ;)

http://kineme.net/composition/dust/LightPaining

laserpilot's picture
Re: Light Painting

Here you go..i hope this still works. Can't attach because I'm too busy to zip at the moment, but here is a link: http://dl.dropbox.com/u/11169/Lightpaint%20simple.maxpat (if anyone ever can't get at this when the link disappears you can email me@ laserpilot@gmail.com)

bAjA's picture
Re: Light Painting

cheers laserpilot for the voice of experience, thats a top tip to restrict the luminance range...

cheers dust for starting off a comp, i can't wait till it gets dark and i can do waving my lighter around ;-)

bAjA

goto10's picture
Re: Light Painting

I reckon this luma key/feedback image filter should also get you on your way: http://www.hybridvisuals.nl/downloads/m8-trace-quartz-composer-effect/