TV’s in a (large) nutshell

I recently rearranged my living room to be a bit more spacious…and the 24" monitor I was using for a TV wasn't cutting it any more.  I thought for a long time I could get away without a TV, but the monitor was looking awfully tiny in the corner … and with friends coming over for Rock Band and other reasons, it was time to take the plunge.

I realize this is a stereotypically male topic, but hey, as I learned recently, the male brain is more interested in visual engagement.  So you'll have to excuse me, but I can't help it … I'm genetically predisposed. =)

The short of what I did was I bought a Sharp LC46D64U 46" LCD TV.  Didn't like it so much, so sold it to a Googler for a fair price and ended up picking up a Panasonic TH-42PZ85U 42" plasma TV.  Very happy with this one.

Read the following and learn what I learned.

Looking at TV's in a store

You should do it, but you need to be aware that stores set the TV's to blow out the color and brightness…basically settings that look OK in a harsh store lighting environment but will look like crap in your home.  Whatever you see on the TV's in a store isn't what it's going to look like in your house or apartment and should be taken with a heavy grain of salt.  If you can, go look at TV's in a darkened or specialized home theater dealer … you'll be better able to judge what you like there.

Black levels

This refers to how "black" your TV really is when displaying a black image.  For an example of ideal blackness, if you were in a completely isolated and unlit room, you would not be able to see a TV displaying a black image.

Of course, in reality, this isn't the case.  You can definitely see TV's in a dark room displaying black.

The reason is that LCD's don't perfectly block the backlight, so light gets through.  Plasma TV's have residual/constant charge in the cells, so they still emit a small amount of light even when displaying a black image (or something close to it).  In general, however, the plasma approach results in better black levels, and the LCD approach is rather fundamentally flawed here.

Contrast

How much of a range of brightness can this TV show?  AKA, what is the difference between the darkest level of brightness the TV can display vs the brightest level?  The more, the better.

Manufacturers like to fudge these numbers, as they do with lots of numbers, by quoting contrast levels obtained by dynamically adjusting the image and backlight based on the content of the image or the ambient lighting.  Usually this is the "dynamic contrast ratio".  This is basically bullshit, but seems to be standard operating procedure these days.

LCD's are beginning to approach plasma constrast ratios, but plasma still takes the win on this one too.

Read this article from Gizmodo for a nice primer, and note the pictures.

Power consumption

Plasma TV's generally consume more power, but not as much as you might think.   Here's why.  The transmissive nature of LCD's mean that the backlight is on all the time.  Plasma TV's, on the other hand, only use power when charging a cell.  The maximum power consumption of a plasma TV, therefore, occurs when the screen is completely white.

Obviously this almost never happens.  So while plasma TV's are rated to consume more peak power, on average, they consume nearly the same amount as an equivalent size LCD.  In reality, the variation between individual manufacturers in power consumption is far more important.  In general, expect around 50-150 dollars in energy cost per year to run your TV. 

Here's a good CNet article about HDTV power consumption that goes into more detail. I did not consider this to be a factor when making my purchase.

http://reviews.cnet.com/tv-power-consumption/?tag=rb_content;rb_mtx  

Weight/Size

LCD TV's are generally slightly slimmer and lighter than their plasma counterparts.  We're talking about a 10-15% difference.  For example, my 46" LCD was around 70 pounds…and my 42" plasma was about the same weight. Interesting, but essentially a non-issue.

Motion Blur

This one is interesting.

On a TV, good motion resolution characteristics are important for tracking small objects and continuing to see fine detail as an image quickly pans or changes.  So while a static image may look great on any particular TV, how moving video looks on a TV is an entirely different story.  Typically, the type of consumers looking for good performance in this area are game players and sports aficionados.

Put another way, under motion, the effective perceived resolution of a display may drop.  Your 1080p display may only look like a 900p display when things are moving.

So let's talk about what causes this.

Poor response times 

LCD's have a reputation for poor motion blur characteristics.  This is largely due to the face that early LCD technology did not have good response time characteristics…that is, the pixels couldn't change to the next color as quickly as the images on the screen were changing. As a result, you would see trailing images or blur.

However, this is largely in the past for LCD's.  At a standard framerate of 60 frames per second,  a new frame is displayed every 16 ms.  LCD's have response times around 5-8ms…some going low as 2ms.

Plasma cells have always switched very quickly, so this has generally not been an issue for plasma TV's.

Sample and hold

I found this one really fascinating.

Let's assume your TV is showing you 60 frames of video per second.   Would it be better for the TV to show you

A. Each image for a full 1/60th of a second

B. Each image strobed instantaneously and precisely 1/60th of a second.

As it turns out, according to the way the human eye works, the answer is B.  Think about it this way.  Any particular image being shown to you is only valid for that instant in time. The longer that image is shown to you for the rest of that 1/60th of a second until the next frame is shown, the more "wrong" it is.  This "wrongness" is perceived as motion blur by the human eye.

This effect is called the sample and hold effect.  The "sample", or image, is displayed and then "held" for the entire 1/60th frame time.  The longer it is held, the more blur your eyes perceive. 

So the answer, obviously, is to strobe the image instantaneously every 1/60th of a second.  Of course, nothing is truly instantaneous, so now we've got issues.  The percentage of time spent displaying the image within the frame time is called the "duty cycle".

Regular LCD's have a duty cycle of around 100%…that is, they show the image for pretty much the entire duration of the frame.  CRT's have a duty cycle of 10%…that's really good!  And p
lasma TV's have a duty cycle of around 25%…which is quite good, but not perfect.

New LCD TV's compensate for this by performing either black frame insertion or frame interpolation.  These features get all kinds of weird trademarked names from each manufacturer, so you'll have to dig and interpret the sales literature to determine what features different TV's are actually offering.

I'm not going to get too deep into this, but black frame insertion basically takes the 1/60th of a second and shows the real image for 1/120th of a second and a black frame for the other 1/120th of a second.  This "clears" the image to the human eye and reduces the duty cycle to 50%.  I like this feature in LCD TV's and the effect is clearly visible to a trained eye.

Frame interpolation essentially makes up intermediate frames for the source material.  Since the TV is actually displaying different images 120 times a second, this also reduces perceived motion blur.  The problem of course, is that those intermediate images aren't real.  As a result, weird artifacts, double images, or haze can be displayed accidentally.  Anyway, some people like this feature, some people don't.  Personally, I am not interested in the potential artifacting that can result from this feature, but it's the hot new thing for 2008.

Poor source characteristics

A lot of content you watch already has motion blur built into the image.  You can verify this by freeze framing or pausing something you're watching.  So detecting motion blur in these cases can be really tricky.

Off angle viewing

LCD's used to be absolutely terrible about this…even going so far as to see the colors invert past a certain viewing angle.  Nowadays, things are much better, but not perfect.  You're likely to seeing dropoffs in brightness and contrast as you move more than 20-30 degrees off angle.

Plasma TV's emit light in an unfocused fashion from the cells in the screen, so there's no off angle viewing issues to speak of.

Depending on where you are planning to put your new TV, viewing angles may or may not be important.  In a big living room or common area, you'll notice the viewing angle issues more.

Latency

This refers to the time between when the TV receives an image vs when it displays it.  This is often referred to as input lag.  Today's TV's perform a lot of image processing to enhance or otherwise tweak the incoming image.   Unfortunately, the processing results in a delay before the image gets to the screen.  Typically, this range anywhere from 0 to 100 ms, although on average you'll probably see latency in the 30-60 ms range.

Letancy is important for competitive/serious gaming because every millisecond between when an event is displayed vs when you react to it counts.  Latency is a non-issue for everyone else since as long as the audio and video are in sync it doesn't really matter when the audio and video get to you when you watch TV or DVD's.

For gamers, the problem is, it's really hard to find reviews that measure this specification scientifically.  As a result, you generally have a lot of well-intentioned but misguided people claiming their sets have no latency, when in fact they are simply completely unqualified to make such a claim.

Fortunately, many new TV's are starting to pay attention to this and are including game modes which significantly cut latency.  Having such a mode is no guarantee that your TV can reduce or eliminate latency, however.  If you a serious gamer, you will need to do a lot of research or do hands on testing.

Burn-in

TV's that display the same image for long periods of time are prone to suffering "burn-in".  Basically, the overuse of the same pixels for a long period of time wears down those pixels unevenly and causes them to look visibly different…usually darker.  This leaves a perceptible afterimage on the screen.

LCD TV's suffer very little from this due to the nature of LCD technology.  Since the backlight is generating all the light and the screen is essentially deciding what to let through, burn-in isn't really an issues on LCD's.

Plasma TV's, on the other hand, excite phosphors to generate light and these phosphors do wear down over time.

Even if an image is displayed on a plasma TV for 48 hours straight, it can generally be cleared by displaying a moving white bar over the screen. (this feature is built into most plasma TV's).

Watching 4:3 content on a 16:9 screen can cause noticable burn-in if done often.  There are features to move the image slowly around the screen to prevent burn-in from occurring.

In summary, burn-in is a possibility with plasma TV's, but a multitude of features exist to compensate for this.

Characteristics under different lighting conditions

LCD TV's tend to have better viewing characteristics than plasma TV's under very bright lighting conditions, such as very well lit or sunlit rooms.

However, you can't really expect any sort of good image under harsh lighting conditions.  If this is your goal, buy some cheap LCD TV's and be done with it.

In controlled lighting conditions, plasma TV's have a distinct advantage due to all the characteristics I've mentioned already.

Resolution

Ah yes…what would an HDTV be without the HD?

Most TV's today come in a 720p or 1080p variety.  The number 720p means that there are 720 rows of pixels on the TV.  The "p" means "progressive", which is just a fancy way of saying that each image is displayed all at once as opposed to displaying every other line, which was the default back in the day.

Putting it another way, the resolution of most HDTV's today is either 1280×720, or 1920×1080.

This excellent article from Carlton Bale has charts showing you at what viewing distance you need to be to benefit from different resolutions.

My opinion? Buying a 720p can get you a big discount on the price, and honestly, most people aren't sitting close enough to their TV's to justify 1080p.  Nevertheless, I feel like 1080p is still the way to go … it's such a fundamental characteristic of the television that I think it's worth going for now, and in the future.

Value

Finally, price.  As it turns out, plasma TV's are very competitive with LCD's strictly in terms of size to cost ratio.  However, plasma TV's are generally not manufactured in smaller sizes because no one has managed to squeeze that many cells into a small display yet.  So you generally won't see plasma TV's at sizes less than 42".

Conclusion

OK … believe it or not, I could go on, but I won't.

As you can see, the chips stack up pretty favorably for plasma TV's.  The image is significantly better in nearly all viewing conditions and pricing is competitive.  Having done some homework, my personal suggestion would be the budget plasma lines from Panasonic, like PZ80U or PZ85U series.  You can pick these up from 1100-1500 bucks in the
42-50 inch range.  They seem to win on multiple fronts at competitive prices, especially if you get a discount deal.  LCD TV's are catching up, but as far as I'm concerned, are clearly not there yet.  Don't get caught up in store or marketing hype … avsforum.com has a thread on practically every TV in existence and is an excellent resource.

I hope this helps someone out there looking to buy a TV.  I really don't consider myself that picky, but you still have to do your background when buying the centerpiece of your living room. 😉

Advertisements
This entry was posted in Uncategorized and tagged . Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s