Introduction: Learning About Motion With Light Painting

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Got a light? Then you're ready for the wonderful world of light painting. Light painting is an incredible way to use a camera to make beautiful art and illusions. Here is just a sample of some of the fantastic possibilities. But now you can use it for the study of motion, physics, and kinetics as well.

Photography has always been a great way to capture a single instance, to freeze a moment in time. In 1878, Eadweard Muybridge famously played with that notion by taking a series of high-speed photographs to see if all four of a horse's feet come off the ground when it gallops. This developed in to strobe photography, which suddenly created something not only beautiful but also the ability to capture more than a moment in a single photograph. We could now look at time and motion compressed.

The neat thing about LED light painting is that we can digest this down to how a single point on an object moves, or multiple points. This is like motion capture, the classroom or home version. And with this, we can learn a tremendous amount about kinetics, physics, and the way things move. I've taken this to my classroom and challenged students to come up with experiments where they can look at a kinetic principle with a blend of science, art, and math.

Light it up!

  • What: Learning about Motion with Light Painting
  • Time: quick to make, too fun to stop experimenting
  • Cost: ~$0.50 per LED set-up
  • Materials:
    • LEDs (different colors, super-bright work well)
    • 3V button cells (watch battery)
    • Tape
    • Blinkies (these rings work well)
    • Stuff to experiment with (wheels, rolls, tubes, cardboard, toys, anything!)

NOTE: For all of the LED photos, they look way snazzier in full-resolution. By clicking on them once, then again when they appear larger, and then a third time on the "original file" link that appears below them, you can see the light paths more easily. :)

Step 1: LED Prep

Your first step is to make your LED circuit, which you can do in seconds. Grab an LED and put the leads on either side of your 3V button cell, and it should light up. YAY! If it's not working, try orienting your LED the other way. Positive and negative matters. Tape it up when it's ready to go!

You can start by experimenting with your camera in a dark room. Turn down the F-stop, the ISO, and turn your shudder speed to something between 5-20 seconds, and try to draw in mid-air. Huzzah! You're light painting. This alone is super fun, but soon we're going to get down with some physics.

If you want a review on LEDs, this Instructable is a great intro.

Step 2: Blinky Prep

For doing some motion and speed tracking, blinky lights are super useful. They'll leave dotted lines wherever you go. I found the cheapest and most accessible to be these bumpy jelly light-up rings that you can find here.

Cut open the ring, and pull out the circuit to reveal the batteries, the LEDs, and the button that turns it on and off. I simply tore off two of the LEDs and ended up with a single LED that is timed to turn and off.

Test it out in the dark with your camera!

Step 3: Experiment: Flying Things

Trajectories of flying things are just fascinating, and often too quick for us to really analyze. There are so many things that you can look at, and the joy is that LEDs can track them all.

For starters, I looked at bouncing a wood ball, and could see its spin after the first bounce with the blue LED.

Next I looked at an amazing principle dealing with center of mass of a rotating flying object, which is that an object rotating through the air will rotate around its center of mass. By finding the balancing point for a spoon, and putting an LED there (green) and one at the end (blue), you can notice the smooth trajectory of the green one in comparison.

Other experiments included watching spinning balloons as well as the trajectory of launched objects out of a toy catapult. With the addition of a ruler, you can look at things like height, distance, and angle of different launches.

What more can you fly?

Step 4: Experiment: Rolling Things

Tape LEDs to the edges of different cylinders and spheres, and watch the way they move.

My first experiment was to use a roll of tape with two LEDs taped along the edge. This created beautiful arcs, exploding with light as each LED came close to the ground. The distance between two peaks or valleys of the same LED is equal to the circumference of the tape roll, which with a ruler, is a neat way to calculate it.

My second experiment was to try different cylinders to compare the difference in radii. After that, I tried spinning a yo-yo, which came out less even than I had initially imagined.

You can add in irregular objects, launch things down ramps at different angles with blinkies, and have a whole range of amazing rolling behaviors recorded.

Keep rolling!

Step 5: Experiment: Spinning Things

Moving from rollers, there is also a ton to look at in rotational motion. I made a set-up with a drill, bolt, and plate to spin LEDs at different radii. There are amazing patterns that happen as you walk horizontally while spinning the plate in different directions. You can challenge others to try to figure out which direction you were walking and with what spin.

Additionally, I tried an experiment looking at rotational velocity by swinging a bat with blinky LEDs at three different locations. By the trails, you can see that the LED farther from the fulcrum was moving faster than those nearer. This is an important aspect when looking at things like rotational inertia and why its rough being at the end of a "crack the whip" line in a roller disco or ice rink. :)

Step 6: Experiment: Motion Tracking With Toys

This is a great warm-up to think about the way complex things move, be they machine or alive. I started with attaching LEDs to different wind-up toys, and seeing the way they move. I challenged my class to figure out which light paintings belonged to which toys (after taking off the LEDs).

If you want to make your own toys, here's how to make a simple wobbling robot or here are a bunch of robots from randofo.

Step 7: Experiment: Motion Tracking With People

The mechanics of we human machines is fascinating. This is akin to motion capture used in games and animation in that we're looking at points on ourselves to see where they go. You'll find some surprising results with different everyday motions.

I taped some LEDs to my toes to look at walking, in which I was struck by the quick toe-drops at the end of a step. I moved the LEDs to my toes and heels, and was interested in the quick rise of the heel as well in a slow walk. Try out comparing this to jogging and running to see the differences.

I also tried jumping, and with the addition of tape measurers you can see how high you can get your feet. I tried testing different jumping styles for height, and later putting LEDs on my head as well to see how hight that gets.

There is so much that you can track with people, so try them all out! If you're in need for ideas, try a ball throw, a dance move, a jump, or a funny walk.

Step 8: Experiment: String and Rope

The grand finale (for now) is looking at string and rope dynamics. There is much that you can look at like with waves, tension, and rotational motion.

My first experiment pictured here was to spin LEDs on a string, and then pull the string to the right. you can see the initial different amplitudes of their orbit, and then them narrowing as they are pulled to the right. This is a neat demonstration of the relationship between movement and tension, and is what gives guitar strings their adjustable tones.

You can also try looking at waves and nodes with longer string, or if you want to get really complex, try out a giant wave model with LEDs.

Step 9: Keep Going!

There is of course an infinite number of experiments you can do with lightpainting that deal with kinetics and motion. Keep experimenting, and I'd love to see what you come up with!

Lightpainting is an incredible art, and I hope this Instructable shed some light on how it could be used for science and math observation, too.

Have a wonderful one, and I'd love to see your ideas, comments, and questions below!

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