Advanced Technology

FFD (Feed Forward)
Overdrive (Response Time Compensation)
        Double Overdrive

        Problems with Overdrive

Response time measurements

        ClearMotiv
        MagicSpeed / Response Time Acceleration (RTA)
        Advanced Motion Accelerator (AMA)
        Over Driving Circuit (ODC)
        Fast Response LC + Special Driving
        RapidResponse / RapidMotion
Overdrive Panel Case Study (AUO 8ms)

AU Optronics Simulated Pulse Driving Technology (ASPD)

 

Sony X-Black
Acer CrystalBrite
 

BenQ Senseye
NEC AmbiBright
Samsung "Magic" Enhancements
Acer eColor Management
LG f-Engine
ColorComp

Dynamic Contrast

        LG.Philips Digital Fine Contrast (DFC)
        NEC Advanced DVM
        APE (AUO Picture Enhancer) Technology
        Acer Adaptive Contrast Management (ACM)
   

Black Frame Insertion (BFI)

 

 

FFD (Feed Forward) – In 2001 NEC started developing new technologies used for their TV panels. This idea is based on the fact that the widest colour change is from white to black, and for this change, the maximum voltage is applied to the transistor. NEC’s idea was to apply twice the voltage in half the time, for example instead of applying 1V over a time of 20ms, they changed it to applying 2V over a time of 10ms. This meant that colour changes would be theoretically reduced significantly, but this technique has never been applied according to NEC. The black > white transitions would remain unaffected as they already had the maximum voltage applied to the transistors. This process is the principal behind today’s ‘Overdrive’ technology:

Overdrive – Also referred to as Response Time Compensation, this technology is based on applying an over-voltage to the liquid crystals to motivate them into their orientation faster. This process forces them to a full white (inactive) to black (active) transition first. The crystals can then drop back down to the required grey level. This is helpful as the rise time of a crystal was always the slowest part (response time = Tr + Tf).
 

Double Overdrive - This was an advancement on the traditional overdrive method, and involves applying overdrive to not only the rise time, but to the fall time as well. This is supposed to improve response time and overall quality.

 

Problems with Overdrive

In doing this over-volting, the response time as a whole is reduced but can unfortunately leaves some colour trailing due to the intervening state that the pixel is forced to make. There is a certain risk of video noise being visible on colour masses. Why? When the image is fixed, there is no problem - the pixels don't change regardless of their values. That's the advantage of LCD. But imagine a subtle colour shading. When a tracking shot in a movie moves through those subtle colours, the pixels have to change from one value to another, but the colours are really very close. Unfortunately, Overdrive temporarily causes a much greater variation in the value of the pixel and since all the pixels don't react in the same way - certain ones being faster than others -the result is that the viewer sees accentuated video noise. There may also be some problems with Overdrive being used on TN panels which use dithering. Dithering is normally invisible to the naked eye if the viewer is far enough away, but Overdrive could amplify the visual nuisance stemming from the strong brightness escaping from the panel during the Overdrive period. In real practice accentuated noise and "overdrive trailing" can be a symptom of poorly controlled overdrive methods and can vary from one model to another.

This technology is used widely to boost the response time between grey > grey transitions, as black > white remains unchanged. This has been an area which has already been pushed to it’s limits recently with the newer panels with speeds of 12ms and 8ms. The improvements in grey transitions however are helpful in producing a faster panel overall as these changes have always been slower colour changes in TFT panels and it is important that the response time is low across the whole range (0 – 255).

One other thing to note for Overdrive (RTC) enabled monitors is that running a TFT outside of it's recommended refresh rate (i.e. not at 60Hz) can lead to a deterioration in the performance of this technology and the panel responsiveness is adversely effected! Read the details here for more information.
 

“Response time”, how do we measure it now?

Unfortunately, manufacturers have panels which are on one hand, clearly faster across grey transitions than previous technologies, but on the other, have panels which have not improved on the black > white change which is the ISO norm for measuring “response time”. They have instead now started to list their panels with a response time quoted as being G2G to show that they have made improvements. If a TFT is listed as a G2G response time, then you can be pretty sure the panel is using some form of ‘Overdrive’. Remember though, the response time, even if it is quoted as G2G, is still only the fastest recorded response time for the panel, and some transitions will still be slower.

Overdrive has allowed several panel manufacturers to improve the response times of their products across grey transitions and there are now some panels available with a as low as 2ms quoted G2G response time (e.g. Viewsonic VX922) and 1ms G2G (Hyundai S90D). More significantly the use of overdrive has really improved practical responsiveness in the other panel technologies allowing P-MVA, PVA and S-IPS equipped models to really offer performance to meet growing gaming needs. Typically there have been several 'generations' of overdriven panels including:

TN Film - 4ms / 3ms, and now 2ms
P-MVA - 8ms generation
PVA / S-PVA - 8ms generation initially, but quickly changed to 6ms generation
S-IPS - 8ms and 6ms becoming more common.


Further Reading: An in depth look at Overdrive can be found here at X-bitlabs, including reviews of many of Samsung and Viewsonic's first offering with this technology. An article at BeHardware about Overdrive can be found here. There is also some information about the technology here at Tom’s Hardware France.
 

ClearMotiv – Viewsonic call their overdrive based enhancement suite ‘ClearMotiv’. Bare in mind that they don’t manufacturer any panels of their own, but claim that the panels they have used have improved response time thanks to several technological changes which they have made with the electronics and hardware of the monitors. The various technologies listed below may be used in part of in combination, it can vary from one screen to another. The technologies available include:

  1. Lower viscosity of the liquid crystals

  2. Reducing the gap between cells by 30%, reported to improve response time by 50%

  3. Impulse Driving Method - applying too much voltage at the start, but then reducing it to the correct level, to kick start the crystals

  4. Advanced Overdrive - they claim this also improves black > white and not just grey changes, but this is debatable.

  5. Backlight shuttering - blinking the backlight off briefly during the liquid crystal cell transition. Used only in LCD TV's at this stage. Designed to reduce perceived motion blur caused by the human eye.

  6. Black Frame Insertion - similar to backlight shuttering, but involves inserting a black frame to hide the liquid crystal cell transition. Designed to reduce perceived motion blur caused by the human eye.

  7. Amplified Impulse Technology – This was originally listed in Viewsonic's documentation as a feature in the electronics of the TFT which dynamically controls the amount of Overdrive being used by the panel. Looking at their current whitepapers suggest it is more linked to their Impulse Driving Method as listed above.

Have a look here for Viewsonic’s documentation about ClearMotiv:

http://www.fastresponsetime.com/en/guide.htm

 

MagicSpeed / Response Time Acceleration (RTA) – Samsung’s own version of RTC / Overdrive technology. They always like to have their very own version of technologies, and to be fair, they are one of the main panel manufacturers in the TFT market. There is very little information available about the technology apart from that it is designed to boost grey transition response times. At the end of the day, this is very similar to Overdrive, and as far as I know, works on the same principal. Some models feature an option available through the OSD to disable RTA, and this can show some noticeable differences in practice between active and inactive states.

Advanced Motion Accelerator (AMA) – BenQ's name for overdriven panels. Where the models also feature Black Frame Insertion (see below), they are referred to as AMA-Z.



 

Over Driving Circuit (ODC) - LG.Philips call their overdrive technology ODC and have used it to boost response times on both their TN Film and S-IPS panel technologies. (Link: LG.Philips page)

Fast Response LC + Special Driving - This the name Chi Mei Optoelectronics give to their overdrive technology and is again designed to "reduce residual image tail" and CMO state this will reduce or even eliminate motion blur

RapidResponse / RapidMotion

NEC's own label for overdriven based displays offering improved grey to grey transitions.

Case Study – AU Optronics (M190EN03 V0) 8ms P-MVA panel
Dell 1905FP vs. Viewsonic VP191B-2


While fundamentally the Dell and the Viewsonic are based on the same AU Optronics panel, the electronics applied by the two manufacturers to utilise the panel are different. Performance of the two monitors will therefore be a little different, but don’t forget that there will be many similarities because of the mutual use of the AUO panel. Viewsonic have implemented their ClearMotiv technology into the VP191B which offers not only the Overdrive which AUO have applied to the panel, but adds most importantly the AIT (Amplified Impulse Technology). This dynamically controls the amount of Overdrive used and is said to help reduce blurring of the image even more.

This is apparent from user observations of the two monitors. The Dell, using no extra features, just the overdriven panel from AUO can show some slight trailing of colours in fast paced gaming. This is because of the intervening state which the liquid crystals are forced to enter as part of the overdrive technology (see above). This isn’t major, but the AIT used by Viewsonic has helped to reduce this a little. So although the panels are the same, the electronics and hardware behind the panel can vary.

 

AU Optronics Simulated Pulse Driving Technology (ASPD)

AUO's 'Simulated Pulsed Driving' (ASPD) technology is designed to solve the issue of motion blur in liquid crystal displays. AUO's Simulated Pulsed Driving (SPD) technology simulates impulse-type displays with the adjustment of pixel driving and scanning backlight to reach a CRT-like image quality in motion picture response time. The technology can greatly reduce motion blur, and enable the image performance to reach optimal levels at 4ms equivalent gray to gray (8ms MPRT). The technology is also known as one of the few technologies ready for mass production and can be applied both to WXGA (1366x768) or Full HD (1920x1080) resolutions. 
 

Sony X-Black Technology

Sony's X-Black / X-Brite technology was developed first of all for laptop panels, which has meant that once they started to incorporate it into desktop displays, they could make the casing and bezels very small and stylish. They've incorporated dual fluorescent lamps to light the displays and to help achieve improved brightness over regular LCD panels. This has helped provide some impressive contrast ratios too (including 1000:1) and the added brightness is being marketed as improving movie playback.

Sony have also researched a technique they've named "reflection reduction technology", in which several layers of coating are applied instead of using traditional Anti Reflective coating (which gives you the matte finish and can lead to some loss in colour, noticeably black, depth). The thickness of each of these new layers Sony use is precisely calculated at one-quarter of the wavelength of light – so very thin! The effect is to cancel out reflections before they get to the front of the display. They've improved the colour reproduction (or so the marketing would certainly have you believe) by ditching the old AR style coating, and the improved brightness and contrast have helped improve colour depth. The removal of the AR coating from the panels has also helped them improve image sharpness according to their marketing.


Sony also claim to have improved the viewing angles of their displays by adding a special film coating filter to the front of the panel, which helps reduce the restrictions on viewing angles caused by the inability of the liquid crystals to respond uniformly. This is perhaps the biggest problem with TN film panels today, as while colour reproduction has improved significantly as has response rate of pixels, viewing angles have deteriorated. Panels like the 8ms Samsung TN film panel (in Hyundai L90D+ etc) are a good example of this trend. With these new improvements by Sony to increase viewing angles, X-Black certainly sounds promising on paper.

Sony also claim to have improved the graphics processor used by the panel, to address commands from the graphics card and convert them to commands to the liquid crystals. They claim the hardware and software improvements they have produced for the graphics processor has allowed resizing of images to be improved as well as colorimetric processing advances.

There are a lot of varying opinions on the X-Black technology and it's reflective nature. Some people say it is fine, but a fair few say that it is too reflective. I would certainly be wary of it, and definitely try and see an X-Black screen or laptop first to see if you think you would be ok with it. This has really been the main gripe with the X-Black technology panels, but be wary of the marketing side of their displays as well. While there are many claimed improvements to models using this technology, the advancements may not be as fantastic as they would have you believe.

 

Acer CrystalBrite

Acer's reflective glossy screen coating is referred to as CrystalBrite and appears on some of the desktop monitors as well as their laptops. The technology offers an ultra-fine, highly polished coating which reportedly allows superior filtering of light and quicker image building. It is marketed as reducing reflection from internal and external light sources, and improve colours and image quality. This includes more vibrant and brighter images via backlight diffusion reduction, as well as superior contrast with minimal ambient light scattering.

 

               
           

 



 

Acer CrytalBrite Whitepaper

 

BenQ Senseye

 

  


The marketing for Senseye says: “A pure digital image enhancement technology that automatically and dynamically improves image quality. And a simple promise of higher definition visuals that are deeper, richer and clearer. Experience Senseye technology today – and come one step closer to the true power of the human eye.”

 
 

The idea behind the technology is to make the colours richer, and more vivid; and the image quality sharper and clearer. The original image signal is processed through three engines:

 

 

In reality the Senseye products merely offer a series of presets which the user can select like “photo, movies, user” etc as well as a sensor chip designed to automatically alter the presets when required. The colours and brightness / contrast are set for each selection, with the “user” option allowing you to change them all manually.

 

The official information about the technology can be found here: http://www.benqsenseye.com/
 

 

NEC AmbiBright

 

Similar to BenQ's Senseye technology, this feature automatically adjusts the backlight depending on the brightness of ambient lighting conditions. For example, if the sensor detects the ambient lighting becoming darker, it reduces the backlight appropriately, which helps provide optimal readability and reduce eyestrain. Further, if desired, you can set the display to automatically enter a power-saving mode when the ambient lighting falls below a predetermined value (i.e. when office lights are shut off at the end of the day), which can significantly reduce energy expenses. When you consider the number of monitors used on trading floors and other display-heavy environments, this brightness function can contribute significantly to a lower total cost of ownership.

 


 

 

Samsung “Magic” Enhancements:

 

 

 


Acer eColor Management

 

    

 

This is Acer's name for their selection of monitor preset modes for variations in brightness, contrast and colours. These options are available on selected models via the 'Empowering Key' which gives the user access to the Acer eColor Management OSD interface. According to the whitepaper, eColor management enables control of the following parameters, depending on the preset chosen:

 



Preset modes available in this suite include standard, text, graphics, movie and user. Ultimately, these remain the standard preset modes you would see from a lot of modern screnes, and may or may not be of much practical use, depending on the individual.

 

Acer eColour Management Whitepaper

 

 

LG f-Engine

LG's f-Engine form part of their monitor range OSD and offers a series of preset modes for adapting colour and brightness to meet varying needs of the user. This gives access to settings for brightness, ACE (Adaptive Color and Contrast Enhancement) and RCM (Real Color Management). RCM provides the following settings: 0 = RCM disabled, 1 = enhancement of green, 2 = enhancement of skin tones, 3 = overall color enhancement. One can quickly recognize how the each of these changes will respectively affect the image appearance since a split screen is shown. The regular color picture is shown on the right side, while the left side lets you preview the f-Engine settings' effects on the displayed picture.

 

ColorComp

This uniformity compensation and correction system aims to reduce any screen uniformity errors to almost unnoticeable levels. ColorComp works by applying a digital correction to each pixel on the screen to compensate for differences in colour and luminance. Each display is individually characterized during production using a fully automated system which measures hundreds of points across the screen at different grey levels. These measurements are used to build a three-dimensional correction matrix for the display screen which is then stored inside the display. This data is used to compensate for the screen uniformity, not only as a function of position on the display screen, but also as a function of grey level. If desired, the ColorComp correction can be turned off in order to maximize the screen brightness.

Dynamic Contrast

 

Several manufacturers have introduced dynamic contrast controls to their monitors which are designed to improve black and white levels and contrast of the display on the fly, in certain conditions. It is supposed to help colours look more vivid and bright, text look sharper and enhance the extremes ends of the colour scale, making blacks deeper and whites brighter. This is achieved by adjusting the brightness of the backlighting rather than any adjustments at the matrix / panel level. The backlighting can be made less intensive in dark scenes, to make them even darker, and more intensive, up to the maximum, in bright scenes, to make them even brighter.

 

The official numbers for dynamic contrast are arrived at in the following manner: the level of white is measured at the maximum of backlight brightness and the level of black is measured at its minimum. So if the matrix has a specified contrast ratio of 1000:1 and the monitor’s electronics can automatically change the intensity of backlight brightness by 300%, the resulting dynamic contrast is 3000:1. Of course, the screen contrast – the ratio of white to black – is never higher than the monitor’s static specified contrast ratio at any given moment, but the level of black is not important for the eye in bright scenes and vice versa. That’s why the automatic brightness adjustment in movies is indeed helpful and creates an impression of a monitor with a greatly enhanced dynamic range.

 

The downside is that the brightness of the whole screen is changed at once. In scenes that contain both light and dark objects in equal measure, the monitor will just select some average brightness. Dynamic contrast doesn’t work well on dark scenes with a few small, but very bright objects (like a night street with lamp-posts) – the background is dark, and the monitor will lower brightness to a minimum, dimming the bright objects as a consequence. Ideally this kind of enhancement shouldn't be used in office work since it can prove distracting or problematic for colour work. However, movies and sometimes gaming can offer some impressive improvements thanks to such technologies.

 

As ever, different manufacturers have their own versions of these technologies including:

 

 

Digital Fine Contrast (DFC)

 

On its initial release, LG.Philips DFC technology was marketed as being able to improve the contrast ratio from a typical level of 700:1 to a massive 1600:1! It is supposed to help colours look more vivid and bright, text look sharper and enhance the extremes ends of the colour scale, making blacks deeper and whites brighter. This is a great benefit to gamers who have issues seeing enemies lurking in the shadows and for photo / cinema users who want to improve colour quality. This technology is called the Digital Fine Contrast engine (DFC) and consists of 3 elements:

The DFC is based on an automatic contrast booster controlled to the Look Up Table (LUT) which is reported to alter the gamma of the pixels, darkening dark areas and increasing brightness of the brighter areas. The CCFL backlight tubes have also been replaced by a new generation which is capable of a wider gamut:

 

 

Advanced DVM

 

NEC feature their dynamic contrast on some of their models including the NEC LCD20WGX2. Ultimately this technology runs under the same principle as DFC, but under a different name.

 

 

APE (AUO Picture Enhancer) Technology

 

  

 

AUO Picture Enhancer (APE) Technology integrates the input image data management and the dynamic backlight control solution. The intrinsic image processing system circuit can dynamically adjust the contrast, sharpness, hue, color temperature, and color saturation to accommodate the particular image. Non-linear image processing can accommodate changes in the dynamics of human perception ideally used to overcome an existing problem with LCD TVs where motion picture tends to lose its accuracy during darker states. This technology provides a vivid and sharp image, retrieves natural colors, and enhances color saturation, details in gray levels, and contrast ratio. With AUO’s Image Processing Technology, customers can better enjoy details of dark and night scenes on movies.

 

 


Features:

 

 

Acer Adapative Contrast Management (ACM)

 

           

 

Acer have their own name for dynamic contrast control as above. They market it as offering improved detail in both dark and light scenes, as well as helping to reduce power consumption.

 

Acer ACM Whitepaper

 

 

Black Frame Insertion (BFI)

 

 

This was first unveiled at CEBIT 2006, and by inserting a black frame between images BenQ / AU Optronics claim this helps "clean" the human eye from the perceived afterglow from retention of images in the brain. They have named this technology, BFI (Black Frame Insertion). BenQ have a close affiliation with AU Optronics and so BFI will be used in some of their range. BenQ use slightly different terminology sometimes which you need to be aware of. They refer to their overdriven panels as having 'Advanced Motion Acceleration' (AMA) but those featuring Black Frame Insertion technology may be referred to as AMA-Z as well. For example, the BenQ FP241W comes in two versions, the FP241W without BFI and the FP241WZ with BFI.

 

 

BenQ comment that even a 0ms TFT would result in perceived afterglow due to the human eye mixing images and introducing blur. This perceived motion blur effect is in large part due to the human visual system and is something manufacturers are trying to overcome on their hold-type displays. This is the reason behind looking at new technologies other than overdrive to help reduce blurring on these screens. Other manufacturers such as Samsung are exploring technologies including backlight scanning but AU Optronics / BenQ are favouring BFI instead.

 

 

There are some misconceptions about the technology and I think it is important to realise that this does NOT mean the screen will be running at 120Hz, or showing 120 fps. In reality, the screen will still function at 60Hz / 60 fps, but some of them will be replaced with black frames. The technology will (at least initially) offer three settings for timing of the black frame insertion allowing the user to find a level they find comfortable. There is also an "off" option if required.