Display motion blur

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Display motion blur, also called HDTV blur and LCD motion blur, is a set of several different artifacts that is frequently found on modern consumer high-definition television sets and flat panel displays for computers.

Causes[edit]

Many motion blur factors have existed for a long time in film and video (e.g. slow camera shutter speed). The emergence of digital video, and HDTV display technologies, introduced many additional factors that now contribute to motion blur. The following factors are generally the primary or secondary causes of perceived motion blur in video. In many cases, multiple factors can occur at the same time within the entire chain, from the original media or broadcast, all the way to the receiver end.

  • Pixel response time on LCD displays (motion blur caused by slow pixel response time)
  • Lower camera shutter speeds common in Hollywood production films (blur in the content of the film), and common in miniaturized camera sensors that require more light.
  • Blur from eye tracking fast moving objects on sample-and-hold LCD, plasma, or microdisplay.[1][2]
  • Resolution resampling (blur due to resizing image to fit the native resolution of the HDTV); not a motion blur.
  • Deinterlacing by the display, and telecine processing by studios. These processes can soften images, and/or introduce motion-speed irregularities.
  • Compression artifacts, present in digital video streams, can contribute additional blur during fast motion.

Motion blur has been a more severe problem for LCD displays, due to their sample-and-hold nature.[3] Even in situations when pixel response time is very short, motion blur remains a problem because their pixels remain lit, unlike CRT phosphors that merely flash briefly. Reducing the time an LCD pixel is lit, can be accomplished via turning off the backlight for part of a refresh.[4] This reduces motion blur due to eye tracking by decreasing the time the backlight is on. In addition, strobed backlights can also be combined together with motion interpolation to reduce eye-tracking based motion blur.[5][6]

Fixes[edit]

Strobed backlights[edit]

Different manufacturers use many names for their strobed backlight technologies for reducing motion blur on sample-and-hold LCD displays. Generic names include black frame insertion and scanning backlight.

  • Philips created Aptura, also known as ClearLCD, to strobe the backlight in order to reduce the sample time and thus the retinal blurring due to sample-and-hold.[7][8]
  • Samsung uses strobed backlighting as part of their "Clear Motion Rate" technology.[9] This was also called "LED Motion Plus" in some previous Samsung displays.[10]
  • BenQ developed SPD (Simulated Pulse Drive), also more commonly known as "black frame insertion", and claim that their images are as stable and clear as CRTs.[11][12] This is conceptually similar to a strobing backlight.
  • Sharp Corporation use a "scanning backlight"[13][14] which rapidly flashes the backlight in a sequence from the top to the bottom of the screen, during every frame.
  • nVidia has licensed a strobe backlight[15] technology called LightBoost to display manufacturers. This is normally used to reduce crosstalk during 3D Vision, which utilize shutter glasses, however, it also eliminates motion blur due to its ability to keep pixel transitions in the dark between LCD refreshes.[16]

Motion interpolation[edit]

Main article: Motion interpolation

Some displays use motion interpolation to run at a higher refresh rate, such as 100 Hz or 120 Hz to reduce motion blur. Motion interpolation generates artificial in-between frames that are inserted between the real frames. The advantage is reduced motion blur on sample-and-hold displays such as LCD.

There can be side-effects, including the soap opera effect if interpolation is enabled while watching movies (24fps material). Motion interpolation also adds input lag, which makes it undesirable for interactive activity such as computers and video games.[17]

Recently, 240 Hz interpolation have become available, along with displays that claim an equivalence to 480 Hz or 960 Hz. Some manufacturers use a different terminology such as Samsung's "Clear Motion Rate 960"[9] instead of "Hz". This avoids incorrect usage of the "Hz" terminology, due to multiple motion blur reduction technologies in use, including both motion interpolation and strobed backlights.

Manufacturer Terminology:

Laser TV[edit]

Laser TV has the potential to eliminate double imaging and motion artifacts by utilizing a scanning architecture similar to the way that a CRT works.[24] Laser TV is generally not yet available from many manufacturers. Claims have been made on television broadcasts such as KRON 4 News' Coverage of Laser TV from October 2006,[25] but no consumer-grade laser television sets have made any significant improvements in reducing any form of motion artifacts since that time. One recent development in laser display technology has been the phosphor-excited laser, as demonstrated by Prysm's newest displays. These displays currently scan at 240 Hz, but are currently limited to a 60 Hz input. This has the effect of presenting four distinct images when eye tracking a fast-moving object seen from a 60 Hz input source.[26]

LED and OLED[edit]

Both OLED and Sony's Crystal LED displays use an independent light source for every pixel, without a traditional CCFL or LED backlight used in LCD. Sony's Crystal LED[27] uses individual light emitting diodes for each pixel, instead of using LED as a backlight. Several displays demonstrated at the CES 2012 have been the first modern high definition television sets to overcome the motion artifacts by selectively blanking parts of the screen.[28] Both OLED and "Crystal LED" technologies also have response times far superior to LCD technology, and can reduce motion blur significantly. However, some OLED's are sample-and-hold,[2][29] which can lead to motion blur.

See also[edit]

References[edit]

  1. ^ Charles Poynton is an authority on artifacts related to HDTV, and discusses motion artifacts succinctly and specifically
  2. ^ a b Eye-tracking based motion blur on LCD
  3. ^ Perceptually-motivated Real-time Temporal Upsampling of 3D Content for High-refresh-rate Displays
  4. ^ Publishing from February 2006 from Sharp discussing LED flashing to reduce temporal retinal blur effects with decreasing on-time duty cycle for the backlight.
  5. ^ PDF describing MPRT
  6. ^ http://scien.stanford.edu/pages/labsite/2010/psych221/projects/2010/LievenVerslegers/LCD_Motion_Blur_Lieven_Verslegers.htm
  7. ^ Philips brochure advertising Aptura backlighting that reduces retinal blurring significantly
  8. ^ Review of a philips Aptura set that discusses Aptura briefly
  9. ^ a b Samsung Clear Motion Rate, including the use of a strobed backlight
  10. ^ User manual for Samsung 81 Series TVs with LED Motion Plus technology
  11. ^ BenQ described "black frame insertion" on FP241VW monitor release in 2006
  12. ^ BenQ describes "Simulated Pulse Drive" which seems to be the same technology but renamed for their newer monitor line announced December 2007
  13. ^ Sharp Corporation scanning backlight
  14. ^ Elite LCD HDTV scanning backlight technology
  15. ^ High speed video of an nVidia LightBoost strobe backlight
  16. ^ Eliminating motion blur using a strobe backlight normally designed for nVidia 3D Vision
  17. ^ Resolving latency issues in HDTV video games
  18. ^ JVC's Clear Motion Drive terminology
  19. ^ LG's TruMotion terminology
  20. ^ Samsung's Auto Motion Plus terminology
  21. ^ Sony's Motionflow terminology
  22. ^ Toshiba's Clear Frame terminology
  23. ^ Sharp's AquoMotion terminology
  24. ^ Evans and Southerland use column scanning laser to eliminate motion blur on their high-end laser projection system
  25. ^ KRON 4 News in Bay Area covers coherent and novalux joint venture laser television project
  26. ^ Prsym creates a laser-excited phosphor display marketed towards the advertising market and allows tiling of smaller displays
  27. ^ Sony Develops Next-generation Display, "Crystal LED Display" Ideal for High Picture Quality on Large screens
  28. ^ Sony technical guy explains how Sony handles motion portrayal in OLED displays
  29. ^ Why Do Some OLED's Have Motion Blur?

External links[edit]