A Plasma panel display has near instantaneous response times on the order of 2 milliseconds. What this implies is that a plasma TV subpixel is only alight for a fraction of a second. Typically, most conventional Plasma TVs display video at 60fps (research has shown that the human eye cannot tell any significant difference in motion and smoothness of videos at higher frame rates). This implies that each frame has to be displayed for 1/60 or 17ms. However, the sub pixels of a plasma TV stay alight only for around 2ms when excited. Thus, to display a single frame for 1/60 seconds, the plasma panel excites the sub-pixels in pulses so as to keep all the pixels bright so that they can continuously display the desired frame.
Thus, for example, a 60Hz plasma panel can have 10 pulses per frame, to display the image. Effectively, the screen is being refreshed 60Hz times 10 pulses/frame which gives us a value of 600Hz. This is what Plasma manufacturers refer to as the Sub field drive refresh rate. If the Plasma panel performs 8 pulses per frame, it gives a sub field drive refresh rate of 480Hz. Now when the displayed frame has to be changed to the next frame, the ultra-fast response times of the Plasma TV sub pixels enables an almost instantaneous transition to the next frame.
As a result, even though only 60 frames are displayed per second by the Plasma TV, the near instantaneous transition between frames drastically minimizes motion blur and image ghosting. While the subfield drive terminology is a bit misleading as each frame is not being updated 600 times a second, it still portrays the inherent advantage of Plasma TVs when it comes to fast moving content due to its near instantaneous pixel response times.
240Hz and 480Hz LCD 3D TVs The truth behind the numbers
In the case of LCD panels, things change drastically. One of the fundamental limitations of LCD technology is that the switching speed, or the time it takes to change the pixel color is quite slow on the order of around 4ms. In addition, this refresh rate is dependent on what color the pixel was showing, and what color it has to update to. The 4ms is only a best case estimate and even on some of the commercial 480Hz panels, many pixels can take much longer to update certain pixels.
As a result, when you are trying to view 60Hz content on an LCD TV, in the case of fast moving scenes where there is a large difference between successive frames. If the LCD panel cant keep up with this (which is usually the case) it gives rise to motion blurring and image ghosting artifacts. While LCD manufacturers have been trying to push the response times of these displays, they are still nowhere close to producing a true 240Hz or 480Hz display that can display all video content accurately and free of artifacts at these high refresh rates.
Instead, what they have chosen to do is use advanced mathematical techniques to interpolate between the frames of a 60Hz video signal to give rise to a 240Hz signal. Keep in mind that a large number of the 240 frames being displayed every second are fake interpolated frames. The idea behind this is that the 240Hz source keeps driving the LCD pixels at a much faster rate, thus allowing for a better transition from one frame to the next. While this is certainly an interesting way to improve LCD displays, the 240Hz or 480Hz terms are somewhat misleading since the screen itself is still not capable of true 240Hz/480hz response times.
Joking apart, the article does not accurately predict the fact that manufacturers turned away from Plasma because it was more expensive to build the TVs and ship them than equivalent LCD TVs. (plasma cannot be put flat on the ground whereas LCDs can).
