How we pulled this shot off:
- To keep the lighting consistent, we covered all of the windows with tin foil. We had several “day light” fluorescent bulbs set up on stands that provided consistent lighting throughout the two weeks the flowers were blooming. That lighting setup works great for multi-day shots because the fluorescent bulbs stay cool.
- The camera is controlled by an intervalometer. Each time the camera takes a picture, a red LED light on the back of the camera illuminates. This light lets you know that the shutter is open. (For this shot, we took 3-bracketed images every third minute.)
- An Arduino Duemilanove controls the whole operation. We taped a photoresistor (a simple light sensor) over the camera’s LED light. The photoresistor reacts to the light emitted from the LED, and creates a signal that the Arduino board can measure when the LED turns on. Each time the camera’s shutter opens while capturing an image, the Arduino board knows it.
- As soon as the Arduino board receives the signal that a photo has been taken, we programmed it to wait for 60 seconds–this delay was added to ensure that the dolly will not move while the shutter is open for long exposures. After receiving the signal from the camera and waiting, the Arduino board activates a high capacity H-bridge called a Spike for five seconds.
- The Spike then powers a 2 RPM gear motor connected to the winch. The winch either pulls or lowers the dolly up or down the curved pipe tracks, which are mounted on top of fully adjustable saw horses. The gear motor runs at a fixed speed, so the duration of its runtime determines how far the dolly will move between shots.
- The robotic control of the dolly manages two variables: the frequency of the shots (set by the intervalometer) and the distance covered by the dolly between each shot (set by the Arduino board). Because the track length is fixed and the runtime of the gear motor determines the distance the dolly moves between shots, the run time essentially dictates how many images the camera will take while traversing the track. A consistent number of images means that the length of the final video will depend only on the runtime of the winch. Thus if we want to create a 10 second time lapse with shots covering three hours or ten days, we only need to adjust the intervalometer. This greatly simplifies the field programming of the dolly.