Double exposure is a technique that originated with film photography where you would expose the same frame of film twice (or more). Film can only be exposed to light so much before it will stop recording information. So the part of the film that was darker after first exposure will be most receptive to the light from the second click. It’s typically good to underexpose both photos, because you are exposing the “film” or “sensor” to light twice.

Be sure to check Sara’s blog and website at http://www.sarakbyrne.com for more information on this and other techniques and to check out her fantastic wedding captures.

This film explores playful uses for the increasingly ubiquitous ‘glowing rectangles’ that inhabit the world.

We use photographic and animation techniques that were developed to draw moving 3-dimensional typography and objects with an iPad. In dark environments, we play movies on the surface of the iPad that extrude 3-d light forms as they move through the exposure. Multiple exposures with slightly different movies make up the stop-frame animation.

Read more at the Dentsu London blog:
dentsulondon.com/blog/2010/09/14/light-painting/
and at the BERG blog:
berglondon.com/blog/2010/09/14/magic-ipad-light-painting/