Home Video Asylum

TVs, VCRs, DVD players, Home Theater systems and more.

why we have overscan and 525: the real reason

The reason we have overscan is because the originators didn't want people seeing "extra" non-image information. They also wanted to make sure that any recording or other studio equipment wouldn't show up on the viewer's set and because people wanted the screen to be filled -- thus TVs usually have 5 - 10% overscan. The area inside of this overscan is a 2-part area called the "safe zone". From the center out: 90% of the screen is the "safe action" area and 80% of the screen is the "safe title" area. This ensures that any action and/or titles will be seen by the majority of sets in use.

The NTSC broadcast signal has 525 lines: it's non-image information (sync, vertical retrace, and closed captioning) that drops the number of actual "image" lines down to 486 analog/480 digital lines.



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