Enter a showroom this fall and you'll find the widest selection of big-screen HDTVs ever, each incorporating different tech. There are hang-on-the-wall plasma and LCD sets, along with DLP (digital light processing), LCD, and LCoS (liquid crystal on silicon) rear-projection TVs. Follow these guidelines: Look for a brightness rating of at least 400 candelas per meter squared (expressed as cd/m2), which is double the brightness of a typical direct-view set. Insist on a contrast ratio (the visual difference between the blackest black and the whitest white) of 400:1.