What does 600Hz Sub Field Drive mean?
You have probably seen Plasma panels 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?
If you have, then this article will answer this question and also teach you the difference between LCD and Plasma refresh rates so that you are better informed when you make your 3D TV purchase.
Sub field drive is a term introduced by Plasma panel manufacturers to combat the growing disinformation being spread by LCD TV manufacturers who were claiming higher LCD Refresh rates and using these claims to bolster false arguments about the superiority of 240Hz or 480Hz LCD panels over 60Hz or 120Hz Plasma panels. While most people in the industry are well aware about the truth behind these numbers, and that they refer to completely different things in the case of LCD or Plasma TVs, the average consumer has been left confused and tends to naively go with the assumption - “Higher numbers must mean better”.
Sub Field Drive – Plasma Panel Basics
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 can’t 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.
This motion interpolation does improve the quality of high speed video content, but it also introduces some artifacts of its own. Many people report that when this is turned on for regular content, it makes the video look cheap or fake, and almost ‘too smooth’. It is advisable to only turn this feature on when you are viewing sports or an action flick on your LCD TV.
Conclusion
Subfield drive is a clever terminology devised by Plasma TV manufacturers to prove to consumers the inherent advantage Plasma panels have over LCD TVs when it comes to pixel response times and screen refresh rates. This directly translates into a better viewing experience for fast moving video content and minimized image ghosting artifacts. While 120Hz, 240Hz and 480Hz LCD technology has certainly come a long way in lowering these issues in LCD TVs, Plasma TVs still retain the upper hand over LCD TVs in this area. Be sure to check our Plasma vs LCD 3D TV Guide for more information regarding the pros and cons of Plasma and LCD technology.
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Comments are closed.
about 3 years ago
Will the new 3-D TV’s that are just now hitting the market be capable of playing the field-sequential 3-D DVD’s that were sold for use only with CRT TV’s?
about 3 years ago
Hi Michael,
That’s an excellent question. While the TVs themselves should be able to display the content, the main issue is with the actual DVD player which will need to read this content and transmit it to the TV in a format that it can display correctly. At the moment, it doesn’t seem like this is supported by the 3D blu-ray players.
Having said that, there are softwares for HTPCs that can be used to hook up your computer/laptop to the TV via HDMI and output the video correctly for 3D pictures.
about 3 years ago
In the paragraph, “Sub Field Drive – Plasma Panel Basics”, the article mentions a plasma’s response time as 0.002 milliseconds. It continues by saying that a frame @ 60 Hz is 1/60 seconds or 0.017ms. Given that the unit for 1/60s is 0.017 seconds, or 17ms, I think the article means a plasma response is 0.002 _seconds_ or 2ms. Still fast, but not nanosecond fast.
Thanks.
about 3 years ago
Hey Berto, Thanks a lot for pointing that out! Looks like I accidentally overlooked that. Of-course, I meant milisecond and not nanosecond response times. The 3D TV manufacturers would kill to have those kind of response times!
about 3 years ago
so i have a samsung plasma,it has a 600hz Sub Field Drive and i was wondering if it can handle 3d?? it is not full hd,its only hd ready.
about 3 years ago
The OP is very informed, but I disagree. I think LCD can accomplish 17ms and maybe slightly better. The article is mostly pointing out that LCD won’t be as fast as plasma which is true. In fact it may be several times slower. However I think it can achieve 60hz, 120, 240, 480. I start to wonder beyond that though. And regardless of interpolated frames, it really doesn’t matter as the brain can’t distinguish between these anyway. The point isn’t to provide real frames, but interpolated ones to for two reasons. One to make transitions more smooth. (and it’s not like some object will suddenly vastly change direction on screen in less than 1/60th of a second anyway). And two to reduce eye strain with shutter glasses for 3d. The slower a shutter glass is, the more you can see the flicker, which creates eye strain. If you have a pseudo refresh of 480, and glasses that switch eyes 480/2 times per second, it will appear much smoother on a larger screen. This is one reason companies like Vizio and HTC are upping their refresh. It’s not all about motion blur, but eye fatique as well.
Another point is that once “motion blur” is reduced to the point that people don’t really notice, it becomes less of an issue. Meaning if you have an LCD that is smooth enough to be considered great, a faster plasma won’t look better in that regard, but will instead look EXACTLY the same to the viewer. So it depends on the quality of the LCD. Another downside of plasma is that after about 5 to 8 years of 3-4 hours a day viewing, it will have notably diminished brightness even though plasma has been improved vastly. However, out of the box, some plasma’s may look better. . So you must decide between those factors. If it’s up to me, I’d rather have one of the best LCD’s. If I don’t see motion blur and it looks great, I’ll also know that in 10 years it has the highest chance of still looking roughly the same as when I got it, rather than having something that degrades as you watch it. And again, I read about the new plasmas, so I know they are are improved, but still…
about 3 years ago
Absolutely fantastic article.
After searching so much on Google, this was the only article that made it perfectly clear what the 600Hz Sub Drive means.
Thanks a ton !!!!!
about 3 years ago
Thanks for demystifying this feature for me. I’m looking forward to getting one of these TVs in my home.
about 3 years ago
Could a “600Hz” plasma display show higher than 60Hz signal? New 3D games can output 60fps per eye, 120 distinct images per second requiring 120Hz. If a plasma display can’t handle a 120Hz signal, and doesn’t do any interpolation effect like LCDs, then the 600Hz label is meaningless, right?
I’m not saying that 120Hz LCD TVs can necessarily handle a 120Hz signal, but they are displaying 120 separate images through interpolation to justify the label (though the effect looks a bit odd). I don’t see how showing the same frame 10 times is anything to wank over, especially when most of these TVs can’t handle 24p blu-ray signals properly.
about 3 years ago
Mike, that isn’t true. This article was referencing 2D Plasmas in 2009 (when it was originally written), that used to display at 60Hz with 10 pulses per frame.
However, the new VIERA GT25 and VT25 series provide 60fps to each eye for a total 120fps (or 120Hz). It should be noted that even though some LED 3D TVs provide 120fps to each eye (240Hz total), this isn’t necessarily a good thing or imply better 3D performance.
They typically suffer from more cross-talk issues because the LCD pixels are fundamentally limited by slower refresh times.
about 2 years ago
Your all too technical for me all I want to know which 3d tv I should buy from your experience to use as a gamer,action movie freak,slow and sport fan. Plasma, Lcd ,Led,Dlp.I know I will check it myself at point of purchase.
I need a dark knight to shield me from the Jokers and Riddlers of this world.
about 2 years ago
Whay ther cannot be a plasma Tv of display size 32 inches or 37 inches ??
about 2 years ago
They don’t make 32 or 37 inch Plasma TVs because they are not economical to make. At those sizes, LCD technology has a much bigger benefit when it comes to cost of production. However, Plasma technology allows much easier size scaling. Hence you will notice a lot more 40-50+ inch Plasma TVs that are very competitive, if not cheaper than LCD TVs in those size ranges.
In any case, I wouldn’t buy a 3D TV smaller than 42 inches if I were you. 3D content does need a larger screen size to provide an immersive experience.
about 2 years ago
For many years, the issue has been pixel dot pitch. LCDs are capable of packing pixels extremely densely. Even the venerable CRT technology which I miss dearly could produce significantly smaller pixels at affordable manufacturing prices. Plasma seems to be bridging the gap in recent years, but you still have to buy a screen at least 40 inches to get a panel with all the flagship bells and whistles.
For this reason, I still have a nice 32″ SONY VVEGA 1080i Super Fine Pitch CRT in my bedroom. Sure, I would love a 1080p display, but I do not want to have to turn my head in bed while watching TV to see the entire screen
It is a real shame you cannot find quality CRTs anymore. Samsung still manufactures some shallow CRTs, but they are not even 1080i native, and have poor focus due to the shallowness of the tube :-\
I have to say though, if all you care about is picture quality, Plasma’s the way to go these days. Great pixel response time vs. LCD, better NATIVE contrast ratio (even vs. LCDs with LED local dimming) and less expensive. The image quality will fade over time, but you can afford to buy two or three high quality plasmas for the price of a good local dimming LCD.