Red Button and Old Boxes
Get flash to fully experience Pearltrees
Overscan is extra image area around the four edges of a video image that may not be seen reliably by the viewer. It exists because television sets in the 1930s through 1970s were highly variable in how the video image was framed within the cathode ray tube (CRT). [ edit ] Origins of overscan Early televisions varied in their displayable area because of manufacturing tolerance problems. There were also effects from the early design limitations of linear power supplies, whose DC voltage was not regulated as well as in later switching-type power supplies. This would cause the image to shrink when AC power 'browned out', as well as a process called blooming, where the image size increased slightly when a brighter overall picture was displayed.