It takes lots of light to deliver bright, crisp images on your rear-projection TV, but that same light leaks through to the screen during dark, Perfect Storm—style gloomy scenes, hindering detail. To darken the blacks, a growing number of LCD and DLP rear-projection-TV manufacturers are turning to mechanical apertures that can limit the amount of light that reaches the screen. HP, Toshiba and Sony, among others, are using a dynamic iris, which automatically narrows like a camera’s aperture to reduce the amount of stray light.