Kids are fun somtimes. I got my 2 and 4 year old into light painting, and I highly recommend it if you can get away with it. As a lazy parent, this is my favorite "arts and crafts" project, because it requires no clean-up.
The first session was with a couple of their light-up toys. Then we moved on to the cats' laser pointer. They both pre-date this blog (and this company), but I may in the future circle back and post the results here. Anyway, both sessions went well, so that was enough of an excuse to go find more toys. I ended up finding some real cheap <5mw (because they are kids, after all) colored lasers. We got a 405nm (purple/blue)*, a traditional 640nm (red)*, and a 532nm (green)*.
I guess I should take a moment to talk about laser safety. We only do this with both parents right there, each responsible for one kid, and we treat it like a gun range. Nobody walks down range without a ceasefire. Lasers are always pointed at eye safe things, even if they are off. Oh, and the most important part - we're done the second either of them starts screwing around or not listening. No amount of fun is worth impairing the vision of a child.
The TV in our living room is a projector, so I already have a perfect neutral canvas (the display screen with the projector off) for light painting. I set up the tripod, cranked the exposure length up to 30 seconds, turned off all the lights, closed the blinds, and this is what we came up with.
First, I call the 405nm purple/blue because it really can be either, just by messing with the color temperature of the camera. I shoot raw (.NEF), so I can futz around with it in post. For example, this is the 405nm at 3000K...
Sure looks like a blue laser.
Here's the exact same image at 9090K...
Looks purple to me.
That same technique does comparatively nothing to the red or green lasers. Here's an image that used all three lasers. First at 4000K, then 9000K...
4000K
9000K
The green is affected more than the red, but neither have moved nearly so drastically as the blue to purple shift. Now, none of this is surprising if you know your light science, right? Still, it's kinda fun to see in a practical** implementation.
Now, on to the fun!
At first I let the kids loose to do with their 30 seconds as they saw fit. These were the results...
ISO 1000 (silly daddy)
First try was a misfire - I left the ISO cranked up from a previous shoot. Scaled it back down for round two...
ISO 100 (much better)
After that, I explained to my kids that you can actually DRAW stuff. As an example, I did this...
The mighty X prevails yet again!
I show the kids the result in the chimp viewscreen, and my 4 year old goes "Ooh, I see. Can I try with the purple one?", which of course I let her do. The result is this...
This is what "organized" looks like to a 4 year old
At this point, we start to team up. I and each of my kids take a different color, and we all go at it at the same time. The first result is the prior color temp example (if you came here just for light science, this post has derailed, and I advise bailing now). These are the rest. Spoiler alert: Just about any color that is attempting to make any sort of a pattern is me.
My dots look like V's because a 4 year old was very bouncy on the couch as she made her purple squiggles.
My second attempt at a tic-tac-toe board is admittedly sub-par. But compare it to those red X's and purple O's!
More dots that look like V's. But I'm getting better - some only look like I's, right?
Her "green monster" chased my "purple princess" around in this one. I didn't realize these needed a narrative to accompany them, but my daughter corrected me.
I poorly planned my 30 seconds and didn't finish my "KS" on the end. Oh well.
I think the next logical step would be to find some programmable servos to move them around and actuators to press and release the buttons. Then I could make all sorts of fun stuff. An intermediate step may be to learn how to program servos and actuators. What about steel wool? Has anybody on the internet ever done a long exposure of that burning?
*Be warned, this site is in China, and one of my credit card companies thought for sure my card was compromised and not only prevented my order, but killed my card. When I did eventually get my order placed, it took damn near a month for this stuff to show up. Don't by any means take these links as an endorsement.
**as in "non-theoretical", opposed to "useful for everyday life"