Frequently asked questions about flashing backlight technologies (scanning backlights, strobed backlights, black frame insertion), including how they work. A: A scanning backlight is a flashing backlight for a LCD display that reduces motion blur caused by eye tracking and movements, during fast motion. A: Motion blur on LCD displays occurs due to several factors, including pixel transitions (changing pixel state, GtG transitions) and persistence (static pixel state).
In many older LCD technologies, pixel transition speed has been the major motion blur barrier. The BlurBusters scanning backlight design aims to overcome the disadvantages, by using ultra-high brightness (e.g. There are several academic papers that explain motion blur caused by eye motion, including eye tracking, and how it is a separate factor from pixel transition speed. Actual number of backlight strobe impulses can sometimes be more than one per refresh on certain types of scanning backlights. No repeated frames in the material, because repeated frames leads to increased perceived motion blur caused by eye-tracking. Fortunately, some new LCD panels have finally become fast enough to eliminate noticeable ghost trails within one refresh cycle (about 16.67 milliseonds at 60 Hz). The emergence of 3D 120 Hz means that LCD panel manufacturers have an incentive to make them refresh more quickly, to allow alternate-frame active shutter glasses operation.
Active shutter 3D glasses on LCD monitors briefly close both shutters (blocks both eyes) during the first few milliseconds of a refresh, when refreshing the screen between eyes. One very short strobe is needed for each point in the display per refresh, similar to phosphor decay in a CRT display, as seen in this high-speed video of CRT scanning. Backlight diffusion also must be well-controlled, to prevent much leakage of light from on-segments of backlight, leaking to the off-segments of backlight. Existing HDTV’s that use scanning backlights, do not have a backlight 10 times brighter than normal.
All three major pre-requisites have now been largely solved for high-performance scanning backlights. A: Thanks to tests on new LCD panels, it has now recently become possible to bypass the pixel transition speed barrier. It is possible to wait for pixels to finish refreshing, and then strobe the backlight after the pixels have largely finished refreshing, but before the next refresh.
The human eye sees the 0.5 millisecond strobe portion of a refresh that is visible, instead of the pixel transition speed portion of the refresh that is now made invisible by a turned-off backlight. Some displays use response-time acceleration technologies such as ASUS Trace Free, which helps eliminate perceptible ghosting completely before the next refresh. The backlight impulses using LightBoost (at the time of this writing) are not nearly as short enough to have less motion blur than CRT.
For example, a camera with a quick shutter speed, or sharp frames generated from a video game. This prevents blurriness built into frames from contributing to motion blur.
Most existing scanning backlights for HDTV’s use frame interpolation to increase the refresh rate before using a scanning backlight to reduce motion blur further. In order to reduce motion blur by 90%, you need a backlight that is dark 90% of the time, and lit only 10% of the time once per refresh. Fortunately, LED ribbons have fallen in price to under $1 per watt, and is less than 25 cents a watt at factory cost. The BlurBusters scanning backlight design is made practical by the existence of inexpensive LED ribbons, that are available for as little as 25 cents per watt, going upwards to a dollar a watt for higher-quality ribbons. These ribbons are easily cuttable using scissors at intervals (with convenient solder pads), to allow multiple shorter ribbons, which can be stacked edge-to-edge for a scanning backlight for a computer monitor.
More expensive variants of these ribbons are now available in 6500K with 80 CRI suitable for backlighting use.
Scanning backlights have the same purpose as black frame insertion. They reduce motion blur by using a large dark period between refreshes. The term black frame insertion generally refers to full backlight strobing (or frame refreshes that are completely black), and scanning backlight refers to sequential illumination of backlight segments in a top-to-bottom fashion (similar to a CRT). A scanning backlight that is dark 90% of the time, is conceptually equivalent to black frame insertion that used 9 black frames for every 1 actual frame. Thus, the scanning backlight attempts to trail behind the top-down refresh by a few milliseconds, in order to prevent illuminating LCD pixels that are still in transition.
It is possible to design a scanning backlight mod for an existing computer monitor that only requires access to the VSYNC signal, which can be obtained at any point in the display chain, or even signalled from the computer (with precise time coding). The original BlurBusters scanning backlight design, driven by an Arduino, only requires access to the VSYNC signal.
This scanning backlight design simply uses a pre-programmed scanning speed in order to keep the top-to-bottom backlight scanning in good sync with the top-to-bottom LCD refresh cycle. A one-time scanning timing calibration can be done at the design-time of the scanning backlight. This adjusts the timing of the scanning backlight sequence relative to the timing of the VSYNC.
A simple moving test pattern can be used while doing these calibration adjustments, to find the point of maximum image quality during fast motion.
What is important is that consistency of scanning backlight operation between consecutive refreshes (VSYNC to VSYNC) remains precise, and no other temporal effects interfere with image quality during scanning backlight operation, such as sub-field temporal dithering. This depends on how the scanning backlight is calibrated, in how soon the backlight strobes after the LCD pixels are refreshed.
Note: Some existing HDTV displays use a scanning backlight combined with motion interpolation to multiply the Hz rate. Squeezing a lot of light output, into a short time period,  just once per refresh is necessary to gain maximum motion blur elimination without using motion interpolation. Doing multiple strobes per refresh, for the same part of the screen, can be equivalent to repeated refreshes of the same frame, which leads to more perceived motion blur. On a good plasma display, the multiple subfield refreshes are compressed into a tiny time period.
For LCD displays, a good scanning backlight aims to do the same by illuminating only once per refresh.
Most common displays use dynamic contrast, which dims the entire backlight for the whole image during dark scenes. More expensive displays utilizing LED backlights, including some HDTV’s that use scanning backlights, use local dimming in the form of a full-array LED backlight.
Some four-figure-priced displays for home theater have a scanning backlight but they generally do not have 90%+ motion blur reduction either, and they have the additional disadvantage of also utilizing motion interpolation which is unsuitable for computer use and games, due to input lag (delay in response to interactive human input).

A possible good candidate for strobe backlight modding is a 1ms TN 60 Hz panel, especially if you are able to overclock the refresh rate. Frame packing is a format that’s a bit confusing to understand sometimes, but see this diagram. Schematic representation of metallothionein (MT) structures that show the two domains in a simplified geometry.
In the present figure are reported the main hypothesized functions of MT (bottom) and a simple scheme of MT gene regulation (top). Cd profiles from Mytilus edulis hepatopancreas cytosol after gel filtration chromatography on Sephadex G-75 performed immediately after extraction (blue line) and after 3 days of storage at ?20 °C (red line).
Cd, Cu, Zn and Fe profiles from Octopus liver cytosol after gel filtration chromatography on Sephadex G-75. Metal profiles from kidney cytosols of young (left) and adult (right) Tursiops truncatus after gel filtration chromatography. The “First MT meeting on Unconventional MTs” organized by unconventional animals is reported in this cartoon. Abstract Metallothioneins (MTs) are ubiquitous low molecular weight cysteine-rich proteins characterized by high affinity for d10 electron configuration metals, including essential (Zn and Cu) and non-essential (Cd and Hg) trace elements. Creative Commons Attribution License (CC BY) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Karen~ Just letting you know how much I look forward to each and every daily graphic email!
However, for sample-and-hold displays such as most LCD’s (see high-speed YouTube video of LCD versus CRT refreshing), an image is statically displayed for the entire refresh. Motion blur caused by eye tracking has become the dominant source of motion blur on modern LCD displays, instead of pixel transition speed limitations.
BENQ) take advantage of a scanning backlight, but only reduces motion blur slightly. Currently, high-performance scanning backlights (90%+ motion blur reduction) are not yet available in any PC monitor. Backlight diffusion between adjacent scanning backlight rows, can also lead to multiple impulses for a given pixel reaching the human retinas. Thus, scanning backlights reduces motion blur during 60fps video games and sports broadcasts (e.g. This formula explains why CRT has far less motion blur than LCD — a CRT display has approximately a 1 millisecond phosphor decay.
LCD display makers have been working hard to clean up as much traces of pixel response (ghosting) as possible before the next refresh. This is to hide as much LCD pixel transitions (GtG, as in Grey-to-Grey) as possible from being seen. Manufacturers have incentive to make LCD displays to refresh individual frames faster with less visible pixel transitions, in order to re-open a shutter (for one eye) in the shutter glasses sooner. In order to do the same with an LCD display, a scanning backlight needs to brightly illuminate only one-tenth (or less) of the display at a time, which means backlight flashes lasting similar to the length of phosphor decay.
A different solution to reduce or eliminate backlight diffusion from being a limiting factor to motion blur elimination, is to use a more rapid scanning backlight pass per refresh, or to use full-panel backlight strobes. The backlight needs to be very bright (at least 10 times brighter than normal) to compensate for the very short strobes. These scanning backlights do not have short strobe cycles, so they do not reduce motion blur as much as a CRT display. LEDs are well suited for scanning backlights due to their fast switching speed and brightness. This means it is now possible for LCD panels to have the same perfectly fluid motion that CRT displays have. In some recently developed LCD displays, the vast majority of pixel transition speed is less than a single frame of a refresh. A single refresh at 60Hz takes about 16.67 milliseconds, and pixel transition speed has now become far less than this. Thus, the human eye no longer sees motion blur caused by pixel transition speed limitations, provided the display is able to finish refreshing before the next refresh cycle.
This now allows motion blur reduction to approach CRT quality for perfect-looking crystal clear fast motion during video games.
However, future LightBoost implementations can achieve this, by cramming an extremely bright 250-watt LED backlight into a 23″ monitor.
There is much less motion blur elimination for movies and low frame rate material (non-interpolated).
Other computer operations, such as smooth-scrolling of text and web browsers, can benefit noticeably from a scanning backlight that allows crystal-sharp moving text. Today’s gaming LCD computer monitors can operate at a 120 Hz native refresh rate, and would be flicker-free (for most people) similar to a 120 Hz CRT display. However, the BlurBusters scanning backlight design does not use frame interpolation, and has none of the disadvantages of frame interpolation. This requires a backlight that is 10 times brighter than necessary for a normal computer monitor.
Actual consumption would be only 10-20 watts because the backlight is strobed briefly, and the actual average lumens will become similiar to a regular computer monitor, but without the motion blur.
Manufacturers already make surface-mount #3528 LED chips for small backlights, and these same LED chips are already mass-produced in ribbon format. It is desirable to illuminate the part of LCD only when that part of the LCD is practically finished refreshing and no longer has significant effects from leftover pixel transitions.
Such LCD panels fast-scan a refresh, as quickly as possible, while both shutters of 3D shutter glasses are closed for the first few milliseconds of a refresh. On some recent modern LCD panels, most of the pixel transitions is complete during the first 2 milliseconds, and human-perceptible ghosting is virtually gone well before the end of the 16.67ms refresh.
The VSYNC signal is a convenient way to signal the start of a refresh, and provides the basis for scanning backlight synchronization.
This resembles a single strobe, even though it consists of multiple rapid strobes in an extremly small time period.
Variants of temporal dithering techniques is used for plasma and DLP displays, but is not used in the majority of LCD’s. However, any backlight, including a scanning backlight, can be specifically designed to also enhance contrast. There are two common backlight methods of enhancing contrast ratio. The average brightness level of the image is converted into a backlight brightness in real-time, every refresh. This does not enhance the contrast between blacks and whites during the same static image, and only enhances contrast between different scenes. One notable exception is the new Sony Motionflow Impulse strobe backlight, which is Sony’s equivalent of LightBoost.

For more information about me, see About Mark Rejhon, and I am also available for consulting services. I am looking to buy a new 3D projector and cannot find out some simple info on ALL 3D Devices in general. So does that mean it DOES support 120hz in (1280×720) 720p BUT only in Frame-packing 3d mode? I have had one other professional person who sells 3D hardware and knows more than me tell me I am wrong. The biological role of these ancient and well-conserved multifunctional proteins has been debated since MTs were first discovered in 1957. Metallothioneins, Unconventional Proteins from Unconventional Animals: A Long Journey from Nematodes to Mammals. We’re doing a vintage themed wedding for my daughter and I stumbled across your site! On faster 1ms and 2ms monitors, pixel transition speed ceases to be a dominating factor after the first few milliseconds (e.g.
The slow pixel transition speed trait of LCD (influences motion blur) is different from the sample-and-hold trait of LCD (influences eye tracking motion blur).
Your eyes are still moving during a refresh, causing the static image in one refresh to be blurred across your retina, before the next refresh steps the image forward in the next frame.
Science has shown that motion blur reduction is directly proportional to the length of impulses.
This reduces measurable motion resolution, because multiple impulses are equivalent to repeated frames.
To ensure these are not limiting factors, the camera shutter speed must be faster at the source, than the length of the impulse at the destination display, and the video should not contain visible compression-related motion blur.
That is between 1 to 2 milliseconds out of a 16.67ms refresh cycle, about 10% of a refresh cycle. Full backlight strobes are also more practical on newer LCD panels that do individual refreshes more rapidly. The important motion-blur elimination factor is that each point in the display is flashed as briefly as feasible, only one strobe per refresh. As observed in the high-speed video of CRT scanning next to an LCD display, phosphors on CRT illuminate extremely brightly for a very short time period — at least 10 times brighter than a typical LCD backlight. In addition, these displays often have a dimmer image when the scanning backlight mode is enabled. LEDs are now available at costs less than 25 cents per watt at factory cost, and prices are continuing to fall. This provides an excellent window of opportunity for a massive motion-blur reduction from a higher-performing scanning backlight. Phosphor decay of most white LED ribbons is less than the phosphor decay of CRT, so phosphor decay of LED ribbons will not be the limiting factor for matching CRT in motion resolution. This is to prevent the majority of pixel transitions from being seen, while waiting for a refresh during alternating between eyes.
Mark Rejhon’s BlurBusters scanning backlight design is designed to be suitable for computer use and games, and does not use motion interpolation. From a motion blur elimination perspective, multiple rapid strobes is equivalent to one strobe lasting from the first strobe to the last strobe. This enhances contrast between blacks and whites during the same  static image. As of year 2012, no consumer computer monitors use local dimming.
I know TV sets only accept an input of 60hz BUT what about the actual refresh rate these units use for displaying 3D content? I’ve tried to add this book to my collection many times over the years, and I finally was able to snag a copy at a decent price. This motion blur factor persists even well beyond 120Hz, which is why even 120Hz LCD’s still have more motion blur than CRT. Many scientific tests have shown that halving the length of strobe impulses per refresh, halve eye-tracking-based motion blur. Also, other factors above, affect actual perceived motion blur reduction, such as backlight diffusion between adjacent scanning backlight sections. While phosphor illumination is near-instant, the phosphor brightness fades more gradually over the subsequent 1 to 2 millisecond time period.
Several models also combine motion interpolation, which is unsuitable for computer and gaming use due to input lag. Finally, the extreme amount of extra brightness can be extremely expensive to engineer into a backlight. LEDs is also now available in mass-manufactured ribbon format, which may lead to cheap assembly and manufacture of ultra-bright backlights.
The ribbons have fallen in prices (if ordered directly from factory) to dimes and quarters per watt, which now make high-performance scanning backlights much more practical today, than it was several years ago. Such panels are more suitable for strobing the entire backlight at once, since the pixel transitions for the entire screen, has settled more quickly and more concurrently throughout the whole panel. This review will focus on MTs in unconventional animals, those not traditionally studied in veterinary medicine but of increasing interest in this field of research. Then right click on it (using the button on the right side of your mouse), this will bring up a box, select “save as” in the box and save it to your computer!
Therefore, the shorter the strobe per refresh, and the longer the black period between refresh, the more motion blur reduction occurs. Strobing the entire backlight at once, have a major disadvantage of more uncomfortable flicker at lower refresh rates. Living in different environments, these animals represent an incredible source of physiological and biochemical adaptations still partly unexplored. A significant factor of motion blur on newer LCD panels is now caused by eye tracking motion. See an animation that demonstrates this clearly. With newer panels, the dominating factor for motion blur is now caused by eye movement, and pixel transition speed is no longer the dominant cause. Motion equivalence factors are, in theory, directly comparable to each other on different displays, provided certain assumptions are followed. However, this becomes a non-issue for most people at higher refresh rates (especially when approaching common frequencies of PWM backlights). The study of metal-MT interactions is of great interest for clinicians and researchers working in veterinary medicine, food quality and endangered species conservation.

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