Next time you're at an art gallery, a presentation, or anywhere with a projector, really glance at the screen a few times. You may notice a streak of red, green, and blue quickly flying by your eyes. You've just noticed the rainbow effect. This is a constant problem with DLP projectors that is being addressed in the form of expensive projectors with DLP chips for each color. However, while some people may not even notice the effect, others can get very annoyed by it. HDBlog warns that if you're going to buy a DLP projector, make sure you try it out first and buy it from a store with a decent return policy. Also, if you're sitting around dropping acid every week, that is a different rainbow effect that is not your projector's fault. Tsk, tsk.
Rainbow Effect [HDBlog]
Browse LCD Projectors [CNET]