Time Exposures

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.

UPS Time Exposures

UPS Time Exposures

UPS Time Exposures

UPS Time Exposures

UPS Time Exposures

UPS Time Exposures

UPS Time Exposures

UPS Time Exposures

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:

camera setup

I applied gaffer tape to the floor so the kids knew the boundaries of where they could perform.

Other Builds

My friend Stephen Cartwright built a similar device based on this circuit design. Being a skilled craftsman, he created a much more refined version:

Stephen Cartwright's RGB Wand

Here are some images he and his wife Amy created: