The new Ultra HD 4K screens have four times the number of pixels as standard High Definition TVs.
CNN: New TVs driven by software and streaming, not pixels
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Also known as "ultra-high definition", the format offers four times the resolution of the current 1080p HD standard and is best appreciated up close, or further away from a mega-sized screen.
BBC: CES 2013: Looking beyond 4k to the TVs of the future