Advanced Look at BFI and the FP241WZ

BenQ's AMA technology has already been used to lower response times across grey transitions to as low as 2ms. However, they have hit the conundrum that even if pixel response times were 0ms, the user would still perceive motion blur around the edges of moving objects. Reducing response time has helped, and thanks to RTC based technologies like their AMA, such motion blur has been reduced considerably since the days of non-overdriven panels of the 16ms generation for example. 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. Hold-type displays are defined by VESA (Video Electronics Standard Association) as those where a pixel state remains as it is, until switched to a different state. In summary this means the operation of an LCD screen will be such that pixels only change when they need to, and there is no need to continually re-draw the screens image as is the process on CRT based displays.

Pixels in an LCD display respond to voltages which command changes in the liquid crystal orientation. The principle behind RTC / Overdrive (or in BenQ's case, AMA) is that the voltage supplied is more than traditionally would be applied, in order to allow the crystals to rotate more quickly to their required orientation. Moving objects would exhibit changes in luminance and the pixels in turn are being asked to change on request as an object moves across the screen. This can result in some delay regardless of the response time, and motion blur is exhibited. Studies on the human visual system have shown that the eye responds automatically to changes  in brightness levels in moving objects, an affect which is called "smooth pursuit tracking" or "spatial-temporal integration" and so not only is there the delay from the pixel response, but perceived problems due to the human visual system. As a very crude example, if a pattern of alternate black and white areas moved from left to right across a screen, our visual system would perceive a grey "ghosting" effect.

The Black Frame Insertion (BFI) powered FP241WZ will follow in the footsteps of the FP241W and it looks like at this stage it will be available in February / March for approximately 100 more than the "regular" addition. The Z model is labelled with BenQ's AMA-Z technology (the Z being exclusive to BFI enabled displays) and also referred to as "Perfect Motion".

First unveiled at CEBIT 2006, BFI is an interesting development from BenQ / AU Optronics. By inserting a black frame every few frames, the technology helps 'clean' the human eye of moving images and in real terms, is designed to improve perceived responsiveness. This process artificially helps cloak the ghosting artefacts from the moving image and the human visual system automatically combines the inserted black frame with the image either side of it.

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.

While investigating ways to improve the appearance of moving images on LCD screens, BenQ decided to follow the route of BFI rather than other technologies like scanning backlight or image interpolation technology like Samsung's forthcoming MPA technology. Displays featuring BFI were promising at CEBIT, but it should be noted that they were comparing the FP231W screen (a 16ms S-IPS panel) with the FP241WZ. An employee of BenQ has recently commented that he has seen the FP241WZ in action against the regular version and noticed some improvements mostly on fast moving panning. The technology will 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.


A look at the FP241WZ and BFI technology is available here at Tom's Hardware France (Nov 2006)

 

Much of this content is derived from the various reviews already available, mostly internationally. My thanks to those sites for some of the content and pictures featured here. Thanks to BenQ for some pre-release Whitepaper information about the FP241WZ and BFI technology.