I have been using this effect to create the whole LightSpin project. I used it mostly because the light gets very concentrated, so I had less problem with light spill on the walls.
Portuguese version, by Fabio Meideiros
Spanish version, by Guillermo Castellanos
If you'd like to translate this tutorial in another language, you can download the psd file. (I will handle the french version...).
This is the effect I used to create the LightSpin project: