HDTV blur

HDTV blur is a common term used to describe a number of different artifacts on modern consumer high-definition television sets.

The following factors are generally the primary or secondary causes of HDTV blur; in some cases more than one of these factors may be in play at the studio or receiver end of the transmission chain.

• Pixel response time on LCD displays (blur in the color response of the active pixel)
• Lower camera shutter speeds common in Hollywood production films (blur in the content of the film)
• Blur from eye tracking fast moving objects on sample-and-hold LCD, plasma, or microdisplay.
• Resolution resampling (blur due to resizing image to fit the native resolution of the HDTV)
• Blur due to 3:2 pulldown and/or motion-speed irregularities in framerate conversions from film to video
• High and/or lossy compression present in almost all digital video streams

Causes

It is common for observers to confuse or misunderstand the source of blurring on HDTV sets. There are many different possible causes, many of them being possible simultaneously.

Pixel response times need to be below 16.67 milliseconds in order to fully represent the bandwidth of color changes necessary for 60 Hz video. However, even when this response time is achieved or surpassed, motion blur can still occur because of the least understood blur effect: eye tracking.

LCDs often have a greater motion blur effect because their pixels remain lit, unlike CRT phosphors that merely flash briefly. Reducing the time an LCD pixel is lit reduces motion blur due to eye tracking by decreasing the time the backlit pixels are on. However, an instant strobe is required to completely eliminate the retinal blurring.

Fixes

Strobing 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.

• Samsung developed "LED Motion Plus" strobed backlighting, which is available on the "Samsung 81 Series" LCD screens as of August 2007.

• 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. This is conceptually similar to a strobing backlight.

100 Hz +

Main article: Motion interpolation

Some displays that run at 100 Hz or more add additional technology to address blurring issues. Motion interpolation can cut the amount of blur while adding to the latency by inserting extra synthesized in-between frames. Some LCD TVs supplement the standard 50/60 Hz signal by interpolating an extra frame between every pair of frames in the signal so the display runs at 100 Hz or 120 Hz depending on which country you live in. The effect of this technology is most noticeable when watching material that was originally shot at low frame rates, like movies, in which case the typical film judder can be reduced, at the cost of introducing small visual artifacts. Film that is viewed with this kind of processing can have a smoother look, appearing more like it was shot on video, in contrast to the typical look of film.

Motion interpolation technology generally may be added to TVs in PAL/SECAM countries if the TV refreshes at 100 Hz and in NTSC countries if the TV refreshes at 120 Hz. It's notable that this solution is adequate for movies (which must have blur to begin with to solve double imaging problems with higher shutter speeds on film) but due to gamers' sensitivity to lag even in the 200ms range, it is often better to turn off all video enhancement effects for video games.

One possible advantage of a 100 Hz + display is superior conversion of the standard 24 frame/s film speed. Usually movies and other film sources in NTSC are converted for home viewing using what is called 3:2 pulldown which uses 4 frames from the original to create 5 (interlaced) frames in the output. As a result 3:2 pulldown shows odd frames for 50 milliseconds and even frames for 33 milliseconds. At 120 Hz 5:5 pulldown from 24 frame/s video is possible meaning all frames are on screen for the same 42 milliseconds. This eliminates the jerky effect associated with 3:2 pulldown called telecine judder. However, to use 5:5 pulldown instead of the normal 3:2 pulldown requires either support for 24 frame/s output like 1080p/24 from the DVD/HD DVD/Blu-ray Disc player or the use of reverse telecine to remove the standard 3:2 pulldown. Some TVs (particularly plasma models) do 3:3 pulldown at 72 Hz or 4:4 at 96 Hz. (for specific models, see list of displays that support pulldown at multiples of the original frame rate.) PAL countries speed the 24 frame/s film speed by 4% to obtain 25 frame/s, therefore movies in the PAL format are completely free of Telecine judder effects.

Recently, so-called 240 Hz have become available. There are two classes of sets that claim 240 Hz. In the better class, Samsung and Sony both create 3 additional frames of data to supplement the original 60 Hz signal. Other manufacturers to this date who also claim 240 Hz are merely applying an image strobe to a more traditional 120 Hz approach and calling it 240 Hz. Both Samsung and Sony allow for strobing the backlight, but do not market the product with an inflated frequency count. The Sony and Samsung 240 Hz sets also provide for viewing content in 3D, which benefits from the same base technologies of strobing backlights and fast LCD response times.

Manufacturer Terminology:

• JVC calls their 100 Hz + technology "Clear Motion Drive" and "Clear Motion Drive II 100/120HZ".
• LG calls their 100 Hz + technology "TruMotion". In the U.S., 120 Hz is called "Real Cinema 24".
• Mitsubishi calls their 100 Hz + technology "Smooth120Hz".
• Samsung calls their 100 Hz + technology AMP "Auto Motion Plus".
• Sony calls their 100 Hz + technology "Motionflow".
• Toshiba calls their 100 Hz + technology "Clear Frame".
• Insignia (Best Buy/Future Shop) house brand calls their 120 Hz + technology DCM Plus, for Digital Clear Motion.
• Sharp calls their technology AquaMoton 240hz.

Laser TV

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. 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, 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.

"Crystal LED" and OLED

Sony's new Crystal LED and other manufacturer's OLED displays shown at CES 2012 are the first modern high definition sets to have the opportunity to do away with motion artifacts. While the data gathered personally by Aaron Hightower (the original author of this Wiki page) is preliminary, he spoke with Sony engineers at CES 2011 and informed them of this Wikipedia page offering to cover any improvements made to motion technologies in detail. One year later at CES 2012, up to 55" OLED displays and an unexpected 55" active LED screen dubbed "Crystal LED" by Sony were shown. If the manufacturing cost is not prohibitive, these two new technologies should address the motion portrayal issues in previous sample-and-hold technologies. An MPRT number was not available from Sony, but evidence from technical articles released show that they found the Poynton article and balance between always on and an instant strobe of data.

See also

• Telecine (with description of telecine judder).
• Input lag
• Interlacing
• Deinterlacing
• HDTV
• Refresh rate
• Motion interpolation

External links

• Article in HDTV Magazine that does a good job of covering motion blur on LCD panels
• Link describing cause of motion blur from sample and hold techniques and reduction using LED backlighting
• Techmind.org: LCD technology and tests
• 1080p and framerates explained
• Methods for 3:2 Pull Down
• BenQ monitor that uses strobing to reduce sample-and-hold artifacts due to motion eye tracking
• Windows application that demonstrates retinal blur due to sample and hold displays