Similar to the rainbow effect found with DLP HDTVs, some people notice a phosphor lag when watching plasma televisions.  HDTVTest breaks it down and explains and how this happens:

Different chemical elements are used in the production of individual red, green and blue phosphor coating in plasma cells. The difference in chemical properties results in a variation in the excitation and decay time: blue is the fastest; green, the slowest; and red in between.

This is also references as the green trail.  Keep in mind that while this phenomenon exists it really boils down to whether or not your eyes notice it.  In reality, most people don’t.

If you are one of the few people who do notice it, there are steps you can take to try and fix it:

lowering the contrast (white level) on your plasma TV

using suitable ambient lighting to slightly reduce on-screen contrast (that’s why phosphor trail tends not to rear its ugly head in brightly-lit stores)

waiting for the luminosity of the phosphors to reduce naturally through normal use

sitting further away from the plasma screen

avoiding black-and-white movies

Don’t let this prevent you from considering a plasma HDTV.  Plasma HDTVs are still known for having the best black levels, as well as been less expensive.

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