Penki

Penki is an app that allows you to paint with light - creating 3D messages and images with an iPhone that are revealed in long-exposure photographs.
See examples of photos made using Penki at http://www.flickr.com/groups/penki.
It's based on the Making Future Magic light-painting film from Dentsu London and BERG.

Penki slices your message into a series of images, which are played back on the phone’s screen - over a long exposure photo, the words and messages are visible when the phone is dragged in front of the camera:

- You'll need a camera that is able to take a long exposure photograph; at least 2 seconds.

- You’ll need to be in a darkened space - it doesn't have to be pitch dark though.

- Initially try holding your phone at 45 degrees to your camera.

- Penki will tell you how much distance you need to cover for your word.

- There’s an audio ‘pip’ for every second of the ‘pass’. They start at the first second, and end with a higher-pitched ‘pip’ for the last second of the pass. For example, for a 5 second ‘pass duration’ you’ll hear 6 pips.

- Pass duration should be matched to the exposure length on the camera, and longer words will need a longer pass duration.

- Try to keep your camera's ISO between 80 and 200; this will make for a less-grainy photo.

- If your camera’s aperture can be controlled, start with the largest aperture you can (e.g. f2.0 - the lowest f-stop number available); move to a higher f-stop (smaller aperture) if the photo produced is too bright.

- The iPhone's screen brightness should be set to about 75% (in your phone’s settings to avoid light spillage obscuring what you’re trying to paint. If using an iPad in 2x mode, this might need to be lower still.

For more instructions and troubleshooting please see penkiapp.com.

Please note that Penki requires iOS 4.0 or above.