# Display motion blur

Motion blur, refers to the following two phenomena: the reduction in clarity when tracking moving objects on a display, as well as the frames "blending" together. The latter is due to the pixels making up the display not having instantaneous response times, whereas the former is the result of the display not showing the frame for an infinitesimally short amount of time: your eyes are "tracking" an object that is in fact stationary, resulting in it looking smeared/blurry. It is important note that this would not happen in real life, where objects can stay crystal clear, even when moving rapidly. I.e. a large change (in degrees or radians, not the absolute speed) of the position of the object in a short amount of time.

## Cause

Displays work by rapidly showing frames, each one slightly different from the previous, thereby creating the illusion of movement. Let's take a normal computer monitor with a resolution of 1920×1080 and a refreshrate of 60 Hz. If an object were to move across the display in 2 seconds, there would be 60×2 = 120 "steps", each one translated by 1920÷120 = 16 pixels. Your eyes, however, would not start and stop, over and over again to track the object, quickly moving the fovea to the "new" position of the object for 1000÷60 ≈ 16 milliseconds, only to do it again and again. Instead, your gaze would move across the display in a fluid motion, following the approximate location of said object. Because your eyes rotate to track something that doesn't actually move in a smooth, continuous motion, the image gets "smeared" across the retina. This mismatch is what causes motion blur, and explains why it doesn't occur when tracking physical objects; unlike the simulated motion on displays, real motion is actually continous, whereas on a display, objects travel in a discrete steps. The experienced motion blur can be approximated purely as a function of persistence, simmilar to the shutter speed when taking pictures, because motion wise, it is actually the exact same thing, just from opposite frames of reference.
Normally, this motion blur due to persistence of vision is undesirable. However, there are devices that entirely rely on this phenomenon to function. So called "POV displays" work by quickly rotating a number of LEDs, turning each one on and off in a calculated position. The circular streaks of light displaying an image are the result of motion blur due to persistence of vision.

## Reducing motion blur

Motion clarity can be improved by decreasing the persistence, which is the amount of time the image is displayed for. Manufacturers use various names for their motion clarity enhancing technologies. Nvidia's implementation is called ULMB, Asus' ELMB, and BenQ Zowie uses DyAc and DyAc+. LG refers to black frame insertion on their OLED TV's as "OLED Motion (Pro)". The "pro" moniker denotes that BFI at 120 Hz is supported, as opposed to being limited to 60.

### Black frame insertion

The key to reducing motion blur lies in decreasing the time the pixel stay illuminated. On liquid-crystal displays, this can be accomplished by strobing the backlight, whereas on OLEDs, this must be done by rapidly turning the pixels on and off, made possible by the fact that OLEDs have response times far shorter than those of LCDs. OLED TVs released 2020 & 2021 utilizing LG's WOLED panels feature black frame insertion at 120 Hz, with a duty cycle as low as 38%, resulting in a mere 3.2 ms of persistence. Due to the BFI, the experienced motion blur is comparable to that of a regular sample-and-hold OLED display running at roughly 310 Hz.

### Backlight strobing

By quickly turning the backlight on and off ("strobing"), the image appears for a shorter amount of time. This reduction in persistence is what reduces motion blur. Different manufacturers use many names for their strobed backlight technologies for reducing motion blur on sample-and-hold LCDs.

### 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 (24 fps material). Motion interpolation also adds input lag, which makes it undesirable for interactive activity such as computers and video games.
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" 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:
* JVC uses "Clear Motion Drive".
* LG uses "TruMotion".
* Samsung uses "Auto Motion Plus" (AMP), "Clear Motion Rate" (CMR), and "Motion Rate".
* Sony uses "Motionflow".
* Toshiba uses "Clear Frame".
* Sharp uses "AquoMotion".
* Vizio uses "Clear Action".

### 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.
There has also been Microvision's Laser MEMS Based Pico Projector Pro, which has no display lag, no input lag and no persistence or motion blur.