Plasma Vs LCD Screens, What is Sub Field Drive ?

Plasma Vs LCD Screens, What is Sub Field Drive ?

I found myself asking this question when looking at TV's.. wish they'd make it easier to choose. Having "helpful" sales people isnt really helpful either.. we know they get XX% slice of the pie, so they'll be pushing the $1500 screen over the $800 every single time.
So I started collating my own list of specifications which are comparable ! Inches are inches, Number of HDMI Ports are Numbers, but how about Refresh Rates & Response Times ?

Thats when I came across Sub Field Drive, and its only applicable to plasma, but what does 600hz Sub Field Drive mean? Read on !

 


If you've been shopping for Plasma panels lately you'll have seen them marked with cryptic terms such as 600Hz sub field drive or 480Hz sub field drive and you’ve probably wondered – What is sub field drive?

Sub field drive is a term introduced by Plasma panel manufacturers to combat LCD TV manufacturers claiming higher LCD Refresh rates and using these claims to bolster arguments about the superiority of 240Hz or 480Hz LCD screens over 60Hz or 120Hz Plasma panels. Most people in the industry are well aware about the truth behind these numbers, they refer to completely different things in the case of LCD or Plasma TVs ! Consumers have been left confused and tends to naively go with the assumption that “Higher numbers must mean better”, and that LCD Refresh is the same as Plasma sub field drive.

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 is only displayed for 1/60th of a second, 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. Subfield drive terminology is a bit misleading as each frame is not being updated 600 times every second, it still portrays the inherent advantage of Plasma TVs when it comes to fast moving content due to its near instantaneous pixel refresh times.