Introduction Manufacturers have been trying for years to improve the gaming experience for users of LCD displays. When they first became widely available and affordable as a desktop monitor solution there were certainly limitations in many areas with the technology. One area which has always been a focus for buyers has been the response time of the display, how quickly the individual pixels can change from one colour to another. For a long time this had a major impact on how the screen can handle fast moving scenes in movies and games and has for a long time been seen as one of the most important specs buyers should look at. Slower panels can suffer from issues like ghosting (trailing images) and high levels of motion blur and smearing. Over the years manufacturers have managed to drive down pixel response times significantly, helping to eliminate a large part of the problem. The advent of overdrive (Response Time Compensation) several years ago signified a step change in pixel response times, driving down grey to grey (G2G) changes and helping to ensure all panel technologies including IPS, VA and TN Film variants could offer decent response times where it was used well. More recently manufacturers have improved gaming again with the arrival of native support for 120Hz+ refresh rates. This has significantly helped improve smoothness and the perceived motion in practice for users, as well as allowing support for higher frame rates and 3D content. One area which has not been as easy to address over the years is the sample-and-hold nature of LCD, which affects the way the human eye perceives the image from an LCD monitor. This is an area which has seen some investment over the years and in this article we will have a look some relatively new technique which can greatly reduce motion blur from LCD's. If you appreciate the article and enjoy reading and like our work, we would welcome a donation to the site to help us continue to make quality and detailed reviews and articles for you.

The Sample-and-Hold Problem LCD displays are sample-and-hold displays and are continuously illuminated, unlike a CRT. The following high-speed camera video of LCD versus CRT being refreshed in real-time gives you a view of how the two differ: The LCD display is continuously illuminated even during refreshes

The CRT display is only illuminated for a short period during refreshes Phosphor illumination is measured in microseconds, upon electron beam excitation. However, phosphor decay takes much longer than that, and can affect ghosting. CRTs can have shorter persistence phosphor which can lead to dimmer images but reduces ghosting, or CRTs can have longer persistence phosphor which can lead to brighter images but more ghosting. On this specific CRT, the phosphor decays within 1-2 milliseconds (to the point where it is mostly dark), so the remainder of the CRT is dark for most of a refresh cycle. The CRT phosphor is many times brighter than the LCD backlight, but for a very short period. The scanning is cycled every refresh very rapidly, 60 times a second on most CRT displays (60 Hz), so it appears as a continuous image to the human eye. Since LCD's are a hold-type display the images are "held" on the screen for the entire refresh. When your eyes are tracking a moving object on a display, your eyes are continuously moving. This means that on a sample-and-hold display, your eyes are continuously moving across static refreshes, which creates the perceived motion blur. This applies even if response times were instantaneous (0ms) and even at 120Hz/144Hz high refresh rate. With modern low response times at a pixel level (1 – 2ms), the actual speed of colour changes is now very fast. Higher 120Hz refresh rates also help drastically with the perceived smoothness of motion and aid the reduction of motion blur. However the issue of motion blur is still there as a result of eye-tracking based motion.


Past Motion Blur Reduction Techniques Various techniques have been tested in the past by manufacturers in an effort to eliminate this perceived motion blur. Instead of using extra Hz, motion blur can also be reduced by inserting black period between refreshes, using various technologies such as Black Frame Insertion (BFI), scanning backlights, and/or full-screen stroboscopic backlights. Some televisions create extra Hz by using frame interpolation (e.g. 120 Hz HDTV's). This is the process of artificially generating intermediate frames, that are displayed between actual frames. However, this is not used for computer monitors due to the input lag and artefacts that frame interpolation creates. Early attempts in reducing motion blur within computer monitors have included some ideas such as BenQ's Black Frame Insertion (BFI) which was first discussed back in 2006. The idea was to insert intermediate black frames in between the normal frames to reduce motion blur. When models sporting BFI were introduced (e.g. BenQ FP241WZ) it seemed the technology had evolved and was instead a scanning