The rainbow effect (RBE) is a visual phenomenon where some people sees flashes of red, blue and green colors on the projected image. This problem is usually associated with older DLP projectors which use a single spinning color wheel to add vibrancy. The wheel spins at a high speed which causes the brain to see the colors together – instead of the sequential way in which it is actually being projected.
While most single-chip DLP projectors use a wheel with the three primary colors (and sometimes a clear area), some models add cyan, magenta and yellow as well.
What causes the rainbow effect?
In certain DLP projectors, the spinning of the color wheel may not be fast enough and some people may end up seeing the different colors flashing across the screen individually. This effect is extremely noticeable when the image is that of a bright object (such as a lit bulb) against a dark background. White (or near white) is made by flashing all the colors in the wheel together, which is what makes the rainbow obvious.
Who are affected?
RBE affects only a small percentage of people and is generally a problem only when viewing video and not static images (such as a spreadsheet). Broadly, people can be classified into three groups: those who are highly susceptible, those who are mildly susceptible and those who don’t notice. To the second group, RBE need not be a deal breaker since many people learn to live with it and treat it only as a minor niggle. But, it is important to remember that even if it is not a problem for you, some of your family, friends, colleagues, etc. may be extremely vulnerable to it.
Are all DLP projectors affected by RBE?
To a large degree, yes. Since all single-chip DLP projectors use color wheels, they are all liable to show signs of RBE. Business projectors which have a 2X color wheel are more susceptible to it than home theater projectors which have a rotation speed of 4X-6X. The higher the speed, the lower the chances of the rainbow effect cropping up. Most new single-chip models use LED bulbs which further cut down on the effect.
To fully eliminate RBE, opt for LCD of LCOS projectors. Three-chip DLP projectors don’t exhibit the effect either, but are on the expensive side.
What is the best way of minimizing the rainbow effect?
If you are only slightly susceptible to RBE, chances are that you will learn to ignore it after a while – even if it is very obvious during the initial period. Sometimes, it becomes more obvious when you move your head. Eating popcorn or any other snack, for example, may make RBE more pronounced, as will moving your eyes quickly across the screen. In any case, the phenomenon is visible only when the scene has a white object on a dark area or vice versa. People who are extremely susceptible to RBE are better off not buying single-chip DLP projectors.