120hz versus 240hz

Yes, quite.

To the OP

If you are seriously considering the purchase of a flatscreen TV of any description, the best advice I can give you is to know what you're asking and seeing in the showroom. Setting aside technical sales mumbo jumbo about refresh rates and so on, you need to understand what you're looking at. There are two basic competing technologies - LCD and plasma. LCD are in general cheaper, but the panel has a slower reponse, which tends to lead to motion blur, so if you are into sports, then you need to see any TVs that you are interested in, displaying this sort of content. Plasma TVs suffer little or no motion blur due to the extremely high switching speed capability of the individual plasma cells in the screen. Plasma panels also do not suffer from any viewing angle issues, which can be a problem with LCDs, particularly if you are thinking of wall-mounting, as most will then need to be angled down towards your sitting position.

You should also be aware that there are several 'resolutions' of screen and drive to take into consideration. Almost all TV showrooms both here and in the US, tend to have the sets running on at least an HD picture, and often a BluRay picture. This makes them look very good at first glance. Problem is that in normal day to day use when you get it back home, you are going to be watching standard resolution terrestrial broadcasts on it, and on many sets, these look pretty dreadful, and it is the reason that so many people are disappointed with their purchase when they get it home, and think that it is not what they saw in the store.

The reason for this is that the actual display panel has a 'native resolution', which is likely to be at least broadcast HD. When you then apply a standard resolution signal to the TV, this has to be 'scaled up' to match its low resolution to the panel's high resolution. This often results in scaling artifacts which may well be much more noticeable as motion artifacts, with fast moving (and sometimes not-so-fast) objects on the screen.

BluRay is a full HD source. This is handled fine by most sets, but be aware that if the TV is just HD compatible rather than "Full HD", then the native resolution of the actual display panel, will again not match the resolution of the signal, and downscaling will take place within the TV to make them match.

So, if you are a film buff, and likely to watch stuff on BluRay, you should consider a set with a full HD panel resolution (1920 x 1080). If it's a large screen you are wanting, consider a plasma over an LCD. Whilst these are still more expensive than LCD, world recession has caused the prices of them to tumble over the last 12 months, and Panasonic give very long warranties with them. When you go into stores to look at them, make sure that you grab an erk to demo properly, any that you are interested in. Make sure that you see a 'standard' definition picture, an HD picture - preferably from a broadcast source rather than from an HD DVD player - and a BluRay picture. If the store claims that it can't show you a standard res picture because they don't have any antenna distribution around the showroom floor (a common claim because they know that a lot of the sets would produce a crap picture on such a source), consider looking elsewhere.

Do as much research as you can before committing and parting with your cash. It really is a much more complex buying exercise, if you don't want to be disappointed, than it was when you were buying a CRT TV set a few years back.

Arfa

CRT TVs refresh at 50Hz or 60Hz (near enough) depending on region.

Since a TV program will only contain images (interlaced) at that rate - or frequently less - a TV that purports to offer a higher refresh rate will have to create the extra images by some kind of interpolation. If it does a bad job, then the result will be unwatchable regardless of how high the refresh rate is.

Sylvia.

But the terms don't have a clearly defined meaning. Indeed, even if they did, the typical consumer probably wouldn't know what they meant. If people buy stuff based on not particularly meaningful, but good sounding, hype, they really have only themselves to blame.

Sylvia.

a

rate is

is

that

Perhaps its a PAL/NTSC thing. Whatever it is all the LCD TVs I've looked at with plenty of action/movement on the screen ,I find as irritating as those digital overlain adverts on hoardings around the sides of TV coverage of football/soccer viewed on CRT TV. But I don't watch soccer so thats no problem to me

To the OP , my advice. Never buy a TV that the seller will only display cartoons on. Try viewing a source showing plenty of greens and dark sections of images and of course fast cross-screen mobvement examples.

Exactly. At least in plasma TVs, the thing producing the light also produces the image.

And if you really want to get picky... I'm not sure it's really plasma. It's ionized gas, and the degree of ionization isn't high enough to be considered a true plasma. I think.

Yes, yes, yes, yes, yes.

Yes, but... I'm surprised at the wide viewing angles of many LCDs, even close to the screen. It no longer seems to be a problem, unless the mishpoche has gathered to watch.

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sets,

is

Yes and no. Most sets do a poor job upconverting 480i to 1080p, and the result can be smeary. The solution is to get cable, with many programs available at native resolutions of 720p or 1080i. The image quality can equal Blu-ray.

aware

native

resolution

It depends. I have a 32" 720p set in my den, and it has no trouble with

1080i signals.

should

...and wanting it you will be...

than

"Home Entertainment" magazine gave a near-frothing-at-the-mouth review to a

48" Panasonic plasma that goes for $1500.

One final point -- don't be overly impressed by the brightest set. Look critically at the image, with a variety of material.

By the way, I've seen the Samsung "LED" set repeatedly at Fry's. I don't like it. I can't quite put my finger on it, but it looks "garish". This might be the way the sample was set up, or it might be inherent. If I were buying an LCD set, it would probably be a Sony.

FYI, Computer CRT screens refresh at 60 to 85 Hz.

The main difference between CRT's and LED's or LCD's is persistance. The CRT's have long persistance phosphors, when they are illuminated, they stay lit for a relatively long time. That's why the interlacing system works, the odd lines are still lit when the even ones are illuminated.

Geoff.

--
Geoffrey S. Mendelson, Jerusalem, Israel gsm@mendelson.com  N3OWJ/4X1GM
New word I coined 12/13/09, "Sub-Wikipedia" adj, describing knowledge or
understanding, as in he has a sub-wikipedia understanding of the situation. 
i.e possessing less facts or information than can be found in the Wikipedia.

It's not that long, which is why photographs of television pictures look so awful. Interlacing is used to avoid flicker without having to transmit 50 or 60 full frames per second.

LCDs don't flicker anyway, regardless of their framerate. The frame rate issue relates to addressing the judder you get as a result of the image consisting of a sequence of discrete images, rather than one that continously varies.

It doesn't help that much TV material that was recorded on film is transmitted with with odd and even interlaced frames that are scans of the same underlying image (or some variation thereon), so that the effective refresh rate considerably lower that the interlaced rate.

Sylvia.

Not quite, otherwise the issue would occur with plasma displays. Indeed, it would with any moving-image recording system.

The problem is that LCDs don't respond "instantaneously". They take a finite time to go from opaque to the desired transmission level, and then back again. The result is that the image can lag and "smear". (25 years ago, the first pocket LCD color TVs from Casio had terrible smear, which added an oddly "artistic" quality to sports.)

For reasons not clear to me, adding interpolated images reduces the smear. This makes absolutely no sense whatever, as the LCD now has /less/ time to switch. I've never gotten an answer on this.

Interlaced images can be de-interlaced. Note that most product reviews test displays for how well they do this.

This is neither new, nor was it invented by Dolby.

It can get more complicated than that. Dolby has a new thing out HDR LCD that on the fly modulates the LED backlights for brightness in groups. that was not possible with CFL LCD backlights.

bob

Yes, that is how it was explained to me from a salesman as well as what I gathered from online info. So, apparently, it is still an LCD screen. Also, somehow the refresh rate of the LEDs create some sort of multiplier effect with the LCDs; thus the higher hz. It sure would be nice to know if this is correct, and also why/how it enhances the picture. Although I am far from an expert in this area (hence my original post), I have the ability to understand just about anything that is explained correctly. When information is presented in an ambiguous way, which is what I have seen so far on internet research, that is definitely a red flag that the author probably is not knowledgable in the subject matter.

Which would be fine if the LEDs corresponded exactly to the pixels. But they don't.

--
*A plateau is a high form of flattery*

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

I've seen at least one review that complained that local dimming produced "halos" around objects in darker scenes. I would never, ever buy a set with such a feature, unless it could be shut off.

A troll?

No it doesn't.

Maybe I'm not picky but those motion artifacts just aren't important enough for me to want to spend thousands on something that doesn't produce them. I have a fairly cheep 32" and while it does produce some artifacts they are insignificant to the overall performance.

Yes, agreed in general, but it does seem to depend a lot on how much you are prepared to pay. The point I was making was that LCD screens tend to be optimised for horizontal viewing angle, and with the supposition that you will be looking directly at the screen, or even slightly down on it, when it is sitting on a conventional lounge stand. When it is mounted on a wall, you will be looking at it from below, and some LCDs - the one I have in my kitchen, for instance - are not terribly good when viewed from such an angle. I had to tilt mine down perhaps 10 degrees, after which, it was fine, so I was just making the point that it's something else to consider *if* the OP was going for an LCD, and *if* he had any intention of wall mounting it.

Again, yes in principle. But not all sets are equal in this respect, and not everyone has access to cable, so it was just one more aspect of the purchasing problem, for the OP to be aware of. I have to say that the 480 upscaling on the Pan plas that I recently bought, is exceptionally good. Although I have satellite here, with a good few genuine HD channels, I also watch many SD sat channels, and SD terrestrial digital channels, and the upscaling to display them on the full HD 1080 panel, is nothing short of excellent.

Again, yes. Downscaling seems to be better handled than upscaling in terms of artifact generation, even on the cheap-end TVs. Again, I was only making the point in an effort to allow the OP to better understand what he needs to be looking for, and asking about, to avoid disappointment with his purchase.

I paid 699 UKP for my 50" Pan plas, so I guess that it's either the same or a similar spec model to the one they reviewed. There are several variants depending on features such as how many HDMI ports, and whether or not they have a built-in sat tuner and so on, but all based on the same basic design. I have to say that I would give it the same "frothing at the mouth" review as your Home Entertainment mag. I spent a long long time looking into this, as I knew that I was going to have a hard job replacing my large-screen Tosh CRT - which produced superb pictures from all sources -with anything flat-screen. I knew all along that it was a plas that I wanted really, but didn't think that I was going to be able to afford one. Now that I've had it a couple of months, there is absolutely nothing - and I really mean nothing - that I could pick fault with, so if you are prepared to look long and hard enough, it is possible to get what you want from this technology.

One other thing that the OP might consider, when he has arrived at a few models that he might be interested in, is to see what he can find out about those models by Googling them, and then looking to see what is being said about them on forums. Many forums have contributors that are hyper-critical and quite brutal with their comments, and I think that there is a lot to be learned from trawling these forums. FWIW, before I actually bought my Pan, I did exactly this, and to my utter surprise, there was barely a single adverse comment world-wide. The only thing that was commented on by a few people was that they thought that SD sources displayed on this set, were perhaps a little 'soft' in terms of contrast, but personally, I didn't find this either on the showroom model that was demo'd to me, or on the one that I now actually have. This sort of thing is another reason to understand what you are asking, and making sure that all these sources and features are shown to you.

Yes, 100% agreed

Yes, agreed on the LED backlit Sammy. I don't like it either, and like you, can't quite put my finger on exactly why ... My mother owned a 37" Tosh for a few months before she recently passed on, and that was as good as I have seen in LCD. I think that if an LCD is the chosen route, it is better to stick to the big far east names

Arfa

Hi!

Yes, I'm sure it is. The only thing that's changed is the way the panel is illuminated so you can see a picture. It used to be that practically all LCD panels were backlight by a fluorescent tube (or a set of tubes).

For a variety of reasons, this has changed. (These reasons would be mercury in fluorescent tubes, lifetime of said tubes as compared to LEDs, complexity of the driving electronics and energy efficiency.)

The "120Hz" refresh rate would not be hard to achieve. An interlaced scanning method produces a picture that (in many cases) appears to flicker much less than a non-interlaced one.

(IBM used to use a similar trick with their 8514 display. It used a

44Hz interlaced vertical scan rate that IBM called an "88Hz" scan rate. It worked reasonably well, as long as you used an IBM monitor with longer persistence phosphors and didn't have anything like a fluorescent light fixture illuminating the room. If you did, the two tended to "beat" against one another and the effect is annoying. And if you didn't use an IBM monitor with the special phosphors, that increased the apparent "flicker" level.)

I don't know how a 240Hz "scan rate" would be achieved. It's probably a sort of trick that the set's electronics use to make the picture seem just that much more stable.

William