Lightpipe The lightpipe is a simple way of showing the audience the effect of the different filter combinations without shining the light from the LED directly into their eyes and blinding them. A quick introduction to the lightpipe technology can be found here. The lightpipe consists of a 20cm long 5cm diameter clear plastic tube. The inside of the tube was coated with 3M optical lighting film which can be obtained by ordering a sample from the 3M lighting division. I left one end of the pipe open with magnets attached to the edge. The other side I covered with 3M Radiant Mirror Film. Radiant mirror film can also be ordered in sample quantities from 3M but you could also use aluminium foil for a similar effect. Both act as a reflector to send the light that reaches the end of the lightpipe back into the pipe. Finally I used a triangular strip of white paper as the extractor (20cm long with one side being 2cm wide and the other tapered to a point). The extractor allows light to escape from the lightpipe and thus improves the brightness of the pipe on the side opposite the extractor (which should point to the audience).