Time Exposures – Project Docs

Published January 11, 2015 by Scott Allen Burns

I had an opportunity to do a project with the University Primary School students back in February of 2012, and this is the result of that activity. I built a seven-color LED light wand that the kids could control. I took time exposures of them as they danced around and flashed different colors. I also had flash units off to the side so I could capture them mid-motion. See below for more details on how I made these pictures.

The LED Light Wand

Here is a video of the LED light wand in action:

It was a quick-and-dirty build, but the final product was definitely functional. Here is a teardown:

The wand comprises the following components:

battery pack (4 AA batteries)
three normally-open SPST switches
three 700 mA constant current modules (BuckPuck model 3023-D-N-700 link)
9W (3 x 3W) RGB LED
thermal tape link
heatsink
ping pong ball (cut open on one end and placed over LED)

They are connected this way:

Stage and Photo Settings

The photos were taken with a Canon HS500 compact camera. Most any camera will work as long as it has manual controls. These are the settings I used:

15 sec exposure
f8 aperture
neutral density filter on
100 ASA

Of course, the camera was placed on a tripod.

During the exposure, I manually triggered two flash units located off to each side. This allowed me to capture an image of the child mid-motion. The strobe units were Vivitar 283s with a Varipower attachment that let me reduce the light output. As I recall (not sure about this), I turned the power all the way to the minimum. I put each flash unit inside a cardboard box to shield the stray light from hitting the camera or the background. I built a trigger switch to fire the flash units.

Here is a layout of the setup: