Harris Shutter
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The Harris Shutter is a bit of a misnomer, being a technique, rather than a piece of photographic equipment.
The effect is produced by re-exposing the same frame of film through Red, Green and Blue filters in turn, whilst keeping the camera steady. This will generate a rainbow of colour around any object that moves within the frame. Some good candidates for subjects include waterfalls (pictured, right), clouds blowing over a landscape or people walking across a busy town square.
Traditionally, the technique is either achieved using a camera that allows in-register multiple exposures, and changing filters on the front of the lens. Another alternative was to make a drop through filter that consisted of the three coloured gels and two opaque sections that is literally dropped through a filter holder during exposure.
With the advent of digital photography, the process has become a lot simpler -- the photographer can simply take three colour photographs on location, and then use software to take the Red channel from one exposure, combine with the blue and green channels from the other two photos to good effect -- this even allows for correction of movement if the camera is inadvertently moved between exposures.
