Editing Backlight (section)

====Backlight dimming====
LED backlight are often dynamically controlled using the video information<ref>LED TVs: 10 things you need to know; David Carnoy, David Katzmaier; CNET.com/news; 3 June 2010; {{cite web |url=https://www.cnet.com/news/led-tvs-10-things-you-need-to-know/ |title=LED TVs: 10 things you need to know |access-date=22 November 2017 |url-status=live |archive-url=https://web.archive.org/web/20171201061250/https://www.cnet.com/news/led-tvs-10-things-you-need-to-know/ |archive-date=1 December 2017 }}</ref> (dynamic backlight control or dynamic "local dimming" LED backlight, also marketed as HDR, high dynamic range television, invented by Philips researchers Douglas Stanton, Martinus Stroomer and Adrianus de Vaan<ref name="USRE42428E">Method of and device for generating an image having a desired brightness; D.A. Stanton; M.V.C. Stroomer; A.J.S.M. de Vaan; US patent USRE42428E; 7 June 2011; https://worldwide.espacenet.com/publicationDetails/biblio?CC=US&NR=RE42428E</ref><ref>LED local dimming explained; G. Morrison; CNET.com/news; 26 March 2016; {{cite web |url=https://www.cnet.com/news/led-local-dimming-explained/ |title=LED local dimming explained |access-date=20 November 2017 |url-status=live |archive-url=https://web.archive.org/web/20171123124120/https://www.cnet.com/news/led-local-dimming-explained/ |archive-date=23 November 2017 }}</ref><ref>Pixel-by-pixel local dimming for high dynamic range liquid crystal displays; H. Chen; R. Zhu; M.C. Li; S.L. Lee and S.T. Wu; Vol. 25, No. 3; 6 February 2017; Optics Express 1973; https://www.osapublishing.org/oe/viewmedia.cfm?uri=oe-25-3-1973&seq=0</ref>).

Using PWM (pulse-width modulation, a technology where the intensity of the LEDs are kept constant, but the brightness adjustment is achieved by varying a time interval of flashing these constant light intensity light sources<ref>Dimming options for LCD brightness; J. Moronski; Electronicproducts.com; 3 Januari 2004; {{cite web |url=http://www.electronicproducts.com/Optoelectronics/Dimming_options_for_LCD_brightness_control.aspx |title=Dimming options for LCD brightness control |access-date=20 November 2017 |url-status=live |archive-url=https://web.archive.org/web/20170728120219/http://www.electronicproducts.com/Optoelectronics/Dimming_options_for_LCD_brightness_control.aspx |archive-date=28 July 2017 |date=March 2004 }}</ref>), the backlight is dimmed to the brightest color that appears on the screen while simultaneously boosting the LCD contrast to the maximum achievable levels

If the frequency of the pulse-width modulation is too low or the user is very sensitive to flicker, this may cause discomfort and eye-strain, similar to the [[Cathode-ray tube#Flicker|flicker of CRT displays]].<ref>[http://forums.lenovo.com/t5/X-Series-Tablet-ThinkPad-Laptops/Flickering-LED-Screen-on-my-X200-Tablet/m-p/111086 Flickering LED Screen on my X200 Tablet] {{webarchive|url=https://web.archive.org/web/20101129221157/http://forums.lenovo.com/t5/X-Series-Tablet-ThinkPad-Laptops/Flickering-LED-Screen-on-my-X200-Tablet/m-p/111086 |date=29 November 2010 }} Post on Lenovo's support forum, 17 March 2009</ref><ref>[http://forum.tabletpcreview.com/lenovo-ibm/22598-migraine-headaches-led-backlighting-x200t.html Migraine headaches from LED backlighting in x200t] {{webarchive|url=https://web.archive.org/web/20110716183008/http://forum.tabletpcreview.com/lenovo-ibm/22598-migraine-headaches-led-backlighting-x200t.html |date=16 July 2011 }} Post on Lenovo's support forum, 12 March 2008</ref>  This can be tested by a user simply by waving a hand or object in front of the screen.  If the object appears to have sharply defined edges as it moves, the backlight is strobing on and off at a fairly low frequency.  If the object appears blurry, the display either has a continuously illuminated backlight or is operating the backlight at a frequency higher than the brain can perceive.  The flicker can be reduced or eliminated by setting the display to full brightness, though this may have a negative impact on image quality and battery life due to increased power consumption.