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.
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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.[2] However, an instant strobe is required to completely eliminate the retinal blurring. [3][4][5]
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 on 35mm film, 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. [11]
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.[12] 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.[13]
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[14] 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.[15] (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:
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.[21] 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,[22] 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.[23]
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