why don't plasmas have a higher refresh rate?

That 120hz, 240hz, 480hz garbage on LCDs/LEDs doesn't make any difference. It's all about the response time, which isn't an issue on plasmas (.2 ms or w/e).

You may notice flicker much more in a retail setting as there are two stimulating factors:

1 - Multiple screens in your peripheral vision.
- This allows your brain to tune into the flicker frequency and greatly improves your detection of said flicker
2 - Having LCDs also present in the same room (as they are 100% duty cycle).
- A reference always provides a giant improvement in detection

Human perception is a very interesting topic.

Plasma displays rely on time to generate enough light and enough gray levels. Reducing the time (increasing the refresh rate) is very limiting in this regard.

Interesting. Do u see flicker with 24fps 3:3 pulldown to 72Hz? How sure are you that u are not seeing interpolation artifacts that gets mistaken as flicker during bright scenes?

PDP technological improvements (high speed addressing, efficiency..etc) have enabled 120Hz to be possible.

However, there is much less of a push to increase the native refresh of PDP for many reasons. The main reason being that manufacturers would rather use the improvements in efficiency for other more important parameters like cheaper/lighter electronics, power consumption, average brightness, black level, 3D..etc. Add to that the fact that PDPs short duty cycle gives it built in motion blur reduction that LCD lacks.

Honestly, flicker reduction is/was an afterthought (but it was researched).

Don't forget those awful fluorecent lights in the store.

There are some differences that may contribute.

CRT
- raster scan
- < 10% duty cycle

PDP
- full screen flash (600Hz compiled into 60Hz "effective")
- ~35% "effective" duty cycle

I was just in Best Buy. I had observed some of the same 'flickering' effects the day before and was perplexed since plasmas advertise 600Hz, so I went back with a buddy of mine to have a look.

I was looking at a Samsung 1080p 50" plasma next to a 240 Hz LED LCD of the same make and approx size. They had some HD 'test' loop going on where they quickly (or slowly) pan across various things such as a crowd in a skating rink (fast pan), and a close up of a globe with lots of fine detail (slow pan).

It was quite obvious that the plasma 'flickered' tons more than the 240hz, and about equally as much as a 60hz LCD that was nearby.

he sales associate explained that plasma refresh rate is actually only about 60 Hz, but that they split the panel into 10 sub-panel, hence the advertised 600Hz.

This was new information for me, but I only started looking into it, however it was a bit disappointing as I had thought the advertised 600Hz was 'way' better than the new 240's.

My friend, you are not alone.

I bought a Panasonic G25 last night and the flickering is driving me crazy. I've been looking for a new tv for 6 months and after being desapointed by many LCD, I decided to give a plasma a try since it seems to answer a lot of the issues I have with the lcd (input lag, screen uniformity, view angle).

My only issue I have right now with the plasma is the constant flickering, espicially on light scenes and screens. it's driving me crazy and starting to give me headache when watching TV.

I too was sensible enough on old PC CRT and always needed to put the CRT on 75hz to feel confortable. I saw some flickering at the store, but you hear it isn't as bad once home. I can tell you, it doesn't change a thing. Sure when you watch a dark scene without bright colors, the picture is amazing, but as soon as you have a very white scene, as soon as there is a commercial with a white display, I ahve the feeling the screen will jump out of the Tv right in my eyes. It's also causing some eye strain so far.

I am about to shoot myself. It seems that I can't seem to find a TV that I like and can live with.

for some reason, I am not having this feeling with an LCD even at 60hz.

I tried a DVD at 48h and it's exactly what I keep seeing all the time, just worst and slower flickering.

Technically Panasonic did not lie when they started using this in marketing but the word "misrepresentation" comes to mind.

The panel does refresh at 600Hz but like I said in my last post it compiles 1 frame from 10 subframes called subfields. Therefore the "effective" refresh rate is still 60Hz.

It was a convenient way to market against 120Hz LCD.

The truth remains that it's a 60hz tv and my eyes are telling me so.

I wish they wold release a 75ish hz plasma or something like that. Would make my life a lot easier.

All European plasmas run at 100hz with frame repeat for this reason. 50hz would be unwatchable.

The truth was always there from the beginning of PDP. Every PDP ever made has been 480Hz or higher (60Hz effective).

Like I said, Panasonic saw an opportunity for marketing.

As mrjktcvs said, fluorescent at 60hz will add to the perceived flickering.

1) Firstly only pulse based displays will flicker like CRT and plasma. LCD are sample and hold so you dont see the flicker but their motion will look wierd when the source fps is low, hence they need techniques to refresh the screens like BFI and MCFI to reduce the hold effect.
2) generally most people do not see flicker on most content around 50/60Hz but you are right that around 75Hz even extreme contents have no flicker for most people. Almost all cannot see flicker around 85 Hz. That is why plasma telecine pulldown is 72/96Hz which is quite optimal already. 120Hz is a good algorithmic convergence for 24/25/30/60 fps content but not very perceivable or useful for plasma realistically, but useful for LCD as explained above.
3) which is why I asked about interpolation artifact cause if the source needs to be converted to 60Hz then the artifact may be perceived as flicker on both plasma and CRT. I don't have sky TV but think u are then using NTSC TV to watch PAL content then. Best if u can feed them with 720p60 materials or blu ray 24p 72Hz mode to reduce processing artifacts and see if u can still see flicker. Essentially you are trying to match the source fps to the display Hz, or at least integer multiples


If 3) is right than u might still see flicker if fed 60 or 24fps content, if you are the unique ones

Plasmas don't have a higher refresh rate because it is not an issue for the vast majority of plasma buyers. It is as simple as that.

gee, never thought it would be this bad to be... special...

anyway, I returned the G25. too bad, I liked the view angle and the blacks on it...

I am flicker sensitive too. I can see it faintly on my Kuro, during bright scenes. I thought it was just me that was sensitive to flicker, but apparantely others are too, just as some are sensitive to rainbows on DLP sets, while others are not. This is one of the reasons that I am looking into an LED for my main set now. Not sure if the flicker would bother me over time.

I understand the feeling. it's bad enough to have this flicker pop up in your face every single time you watch a bright scenem

Incorrect. Weird looking are CRTs and plasmas at low FPS also, because they will display several times the same frame effectively producing retinal persistence.


Plasma's flickering is a different beast than CRT's one. The flickering in plasmas occur on high brightness because of the way PDP produces colors and brightness. PDPs do pulses with varying times to produce the pixels and for higher brightness they need to let more light out from each pixel, that means that they must pulse slower. Higher brightness means more and longer (slower) pulses, lower brightness means shorter and fewer (faster) pulses, hence the flickering in bright spots on plasmas.

CRT's have uniform flickering and uniform refresh rate that's why CRT's have worse flickering on low refresh rates (<85hz) than plasmas, but on higher refresh rates where the human eye can't perceive the brightness changes they are effectively and practically static.

Real static are LCDs, because they have the backlight constantly outputing light so there are no brightness changes between the frames. (Strangely thought not all of them are entirely static. I have a Samsung 305T LCD Monitor and with a video camera I can see that the colors, not the brightness, do some flickering but I have no idea why.) But this produces retinal persistence and because of the slow response time of the crystals that they have, they produce extra motion blur.

Guys do update us if you still see flicker at 720p60 @60Hz or 1080p24 @72/96Hz.

Nektarios, technically plasma do not leave sufficient retina persistence due to luminence drop for each frame.


And technically flicker in CRT should not be uniform as luminence output is different across the screen but is perfect for human perception, which form the basis of gamma correction. Not sure how plasma handle the human perception adjustment though.

PDP flicker has nothing to do with the subfield pulse "rate". The flicker is caused by the subfield order and subfield brightness being sequential. This produces a dark portion and bright portion of each refresh time period. This produces an "effective" duty cycle of ~35%. If you'd like I could post a few sources confirming this.

As for brightness, we percieve more flicker at higher brightness in any flicker producing display. There is a few good papers on this subject which plot brightness and flicker perception.


IMO CRT's may produce worse flickering due to the shorter duty cycle and higher average brightness. Even more significant may be the raster type scan of CRT versus the full screen flash of PDP. I feel raster may be easier to spot.



LCD duty cycle is 100% and our retinal persistence can produce significant blur when "tracking" movement on an LCD. People tend to forget that it is the conflict between our "moving" retina and a "static" object on the screen. The duty cycle then determines the severity of the blur on our retina.

Edit: In this age of variable refresh frequencies (60 up to 240Hz) the term duty cycle should be replace by "hold-time" which is accurate for any refresh frequency.

I didn't know that, I thought that they work with varying pulses to control brightness. So you are saying that they flicker even on low brightness?


Yes I agree about the eye-tracking problem but that is not motion blur, it is judder. You can have judder with a CRT with a refresh rate of 120hz but with a video running at 24 fps. This is because it must redraw each video frame 5 times and that is causing judder to the eye tracking.

LCD Motion blur is caused by the slow response time of the crystals. On an LCD with 120Hz refresh rate (real input refresh rate not the 120hz/240hz interpolation) running a 120 real fps video you see a fading blur/trailing behind the mobing objects because of the slow response time.

Philips on its newest lcd models have real 1ms panels (sharp?) and I have seen it playing high framerate videos with 120hz/240hz interpolation with absolutely no motion blur and no judder, just like a CRT. Besides it there were other LCD models with the same input and with 120hz/240hz interpolation but having motion blur.

I just really hope they make a pc monitor out of that panel.

The same flicker frequency remains but it is significantly less noticeable due to the smaller amplitude.


It is not judder it is motion blurring. In modern LCD displays (with single digit response times) the primary contribution of motion blur is the hold-type problem (100% duty cycle). This has been ubiquitous throughout literature for many years now. Below is an excellent graphic describing the issue.






I can't comment on this as I have not seen this demo.

From what I understand LCD response time need to take with a pinch of salt cause the crystal may respond in say 3ms but they do so in step function and gradation/ grey scale suffer as a result, hence contributing to motion blur. So it is hard to say which problem did Phillips fix since at 3ms you can already refresh at 240Hz mathematically. But LCD definitely need high fps input or interpolation to reduce hold effect blur unlike plasma. It is technically not judder due to source or processing/telecine but the result of retina persistence from hold effect.

I would suggest that the same high framerate input into a theoretical 120 Hz plasma will have only marginal improvement.

I tested out a 30p source file on my Panasonic G25 (recorded a game using Fraps), and I also noticed a slight stuttering. Not as bad as 3:2 pulldown, but I still noticed it. Even though 30 divides into 60 which I don't think would need the 3:2 pulldown thing.

I wonder what causes flicker if the source file divides into 60 evenly? If it were the 60 Hz, I would see it everywhere, but I only noticed it during panning. I was told the panning stutters were caused by 3:2 pulldown, but this is a 30p which divides evenly into 60.

Could it have anything to do with my vision? Or is it the TV? Just want to rule some things out.

It could just be that the pan was too fast. 30p and 24p video will still look "choppier" than 60i/60p video.