page_title: Refresh rate
section_title: Cathode ray tubes
hierarchical_section_title: Refresh rate / Physical factors / Cathode ray tubes
caption_attribution_description: This shows a television scan beam as it refreshes the screen. 1/3000 second exposure. I am the creator of this image, including the image displayed on the TV.
context_page_description: The refresh rate is the number of times per second that a raster-based video display device displays a new image. This is independent from frame rate, which describes how many images are stored or generated every second by the device driving the display.
  On cathode ray tube displays, higher refresh rates produce less flickering, thereby reducing eye strain. In other technologies such as liquid-crystal displays, the refresh rate affects only how often the image can potentially be updated.
  Non-raster displays may not have a characteristic refresh rate. Vector displays, for instance, do not trace the entire screen, only the actual lines comprising the displayed image, so refresh speed may differ by the size and complexity of the image data.
  For computer programs or telemetry, the term is sometimes applied to how frequently a datum is updated with a new external value from another source.
context_section_description: Raster-scan CRTs by their nature must refresh the screen, since their phosphors will fade and the image will disappear quickly unless refreshed regularly.
  In a CRT, the vertical scan rate is the number of times per second that the electron beam returns to the upper left corner of the screen to begin drawing a new frame. It is controlled by the vertical blanking signal generated by the video controller, and is partially limited by the monitor's maximum horizontal scan rate.
  The refresh rate can be calculated from the horizontal scan rate by dividing the scanning frequency by the number of horizontal lines, plus some amount of time to allow for the beam to return to the top. By convention, this is a 1.05x multiplier. For instance, a monitor with a horizontal scanning frequency of 96 kHz at a resolution of 1280 × 1024 results in a refresh rate of 96,000 ÷ (1024 × 1.05) ≈ 89 Hz (rounded down).
  CRT refresh rates have historically been an important factor in videogame programming. In early videogame systems, the only time available for computation was during the vertical blanking interval, during which the beam is returning to the top corner of the screen and no image is being drawn. Even in modern games, however, it is important to avoid altering the computer's video buffer except during the vertical retrace, to prevent flickering graphics or screen tearing.
caption: Electron beam in the process of scanning an image
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