[Edited to add something I inexplicably missed, viewing distance, and also some more links.]
So.
The majority of the questions people ask are about the meanings of several of the often-quoted statistics about HDTVs. Here's a handy-dandy short list of the major ones, and what they mean to you.
1. Refresh rate: These can range from 60Hz to 600Hz. Higher is better, to some degree, although this tends to top out, realistically, at about 240Hz. The number represents the number of times per second that the TV re-draws the entire image on the screen. The higher that number, the smaller the amount of blur around the edges of moving objects. The sole exception to this is in reference to plasma TVs, because their refresh rate works differently than the refresh rate on an LCD TV.
On an LCD TV, if the refresh rate is 120 Hz, that means it redraws the entire screen 120 times per second.
On a plasma TV, it draws the screen (typically) 600 times a second - but only refreshes the actual IMAGE 60 times per second, redrawing each frame of the image 10 times. Which means that a 600Hz plasma = a 60Hz LCD for the purposes of reducing motion blur. Any LCD over 60Hz will look better than a plasma, unless you're planning to spend $2000 on the plasma and $400 on the LCD.
2. Contrast ratio: This is a measurement of the difference between the brightest color and darkest color the TV can display. (Pixel "full on" versus pixel "full off.") Again, the higher the better; with a high contrast ratio, the TV will make dark colors look darker, and bright colors look brighter, without bleed-through or blurring.
3. Inputs: These are the number and type of connectors your TV has to attach other devices. The more, the better, although the legacy device inputs, such as component, composite, and coaxial, are less relevant, as the older devices cannot display HD resolutions anyway.
4. Resolution: Don't believe the lies. There are two, count 'em, TWO, actual, full HD resolutions. 720p and 1080p. There are a host of other resolutions (720i, 1080i, 480p, 480i) but the only two true HD resolutions are 720p and 1080p. Currently, 1080p is the best picture you can buy. If you're comparing two TVs, both are 1080p, and the salesman points at the other one and says "but this one has FULL HD," he's just trying to upsell you to something more expensive. 1080p is the best; there's nothing better; if you have 1080p resolution on your TV, you have all the HD there is.
What do the numbers mean? It's actually not as complicated as you might think. TVs make pictures by drawing tiny dots on the screen; the higher the number of dots, the better the picture. the resolution number is the number of dots the screen can draw along the vertical axis. 1080p, therefore, is a resolution of 1920×1080 dots on screen, for an approximate 2.1 megapixels of picture (to use digital camera terms. Different post.) 720p equates to 1280×720 pixels, or 0.9 megapixels.
If anyone wonders why a 14.1 megapixel camera can only take 720p video, that's a goooooood question.
What do the letters mean? I stands for "interlaced," and P stands for "progressive." (As a note, for a visual demonstration of the difference, click the progressive scan link; there's a graphic.) An interlaced picture means the screen takes turns drawing the picture, drawing the even-numbered horizontal lines half the time, and the odd numbered horizontal lines the other half of the time. This means the TV doesn't have to work as hard - and also means you get way, way, way more motion blur, because you're effectively getting half the refresh rate. A progressive picture means the TV draws ALL the lines on screen with each screen refresh, reducing motion blur and making for a far better picture quality.
Now, we move on to some of the other questions I get asked a lot.
What the heck is the difference between HDMI cables? Answer: effectively, nothing. Unless you spend literally thousands of dollars on your TV to get the absolute highest end options available, there is absolutely nothing your TV can display with the $70 Monster cable some retailers will try to shove up your nose that your TV won't display with the one you get for $3.50 from Monoprice. This is digital broadcasting, guys; either your TV is displaying all the picture there is in the signal, or you get the bouncy box on-screen that says "No Signal."
There ARE some differences, but they only come into play on the very highest-end TVs, and the $3.50 cable is rated to support those features... So any salesperson trying to argue that you'll get a better picture from the more expensive cable is flatly lying to you. (Although, to be fair, they may not know this either.)
What's the difference between plasma, LCD, and LED? This is very common, and a good one, with a simple answer: Lighting. A plasma TV, simply, is a sheet of gas trapped between two panes of glass, that displays a picture when it is ionized; they burn huge amounts of power, are fragile, typically lower resolution than LCDs unless you pay a fortune for them, suffer from screen burn-in (where an image stays on screen even after you turn the TV off,) and generally only have one advantage over LCDs, which is price - you can get a 50" plasma for about the same price as a 40" LCD, although why you'd want a 50" 720p TV is utterly beyond me.
LCD and LED TVs are both liquid crystal displays. It's basically a pane of industrial crystal which displays an image when you send an electric charge through it. The difference between the two is the lightbulbs involved.
...I know, right?
But seriously, the TVs marked "LCD" are lit using the same CFL bulbs they're trying to force you to buy and use in your home lighting fixtures now. They're typically rated for 11 years of "continuous" use, defined as 5 hours a day, every day. They typically use about $30-35 bucks in electricity over that span of time.
The LEDs now... They use light-emitting diodes to light the screen, which offer some huge advantages and one equally huge disadvantage. First, they're lighter and thinner than regular LCDs, which means they require a lot less in the way of hardware to mount them; they burn about half the power that LCDs do - $18/year, versus $35 for the same size - and they are much longer-lived; LEDs typically are rated for 22 years of "continuous" use. They're also capable of more accurate colors; LEDs are monochromatic, releasing light in much narrower color bandwidths than the CFL bulbs do. They're also significantly more expensive than LCDs, costing as much as $100 more for even a small TV than the regular LCDs.
They're worth it; if you can afford it, the LED TVs are the best of the bunch right now.
[Edited to add] How big a TV do I need? This one, oddly enough, involves math. See, the size of TV you should get is based on how far you are from it when you're watching. There's a pair of calculations to do.
First, find the distance from your seat to the screen in inches. For example, mine is about 8 feet - 96 inches. Then you take that distance and measure off a third of it. 96" * .33 = 31.68 = 32 inch screen is the smallest you want to get for my living room.
Then you start over and take your viewing distance and divide it in half. 96" * .5 = 48 = 47" screen is the biggest you could comfortably watch in my living room. So, an 8 foot viewing distance means you should buy a TV between 32" and 47", no bigger, no smaller. In our case, we're shooting specifically for a 37", because at that size we can afford a much nicer TV than we could if we went up to the 42" size.
I will note here that some sources recommend using 2/3 of the viewing distance as the maximum screen size. I don't, because a 63" TV in my living room would cause people's heads to explode.
I will also note here that this changes if you are coming from a standard, 4:3 aspect ratio TV to a widescreen for the first time, and is VASTLY different for a front-projection TV.
Which manufacturer is the best? Unlike the others, this one is mostly opinion. Samsung. I will, however, offer some evidence to support my opinion here.
I am quoting, here: " Samsung customer service said their TVs are repairable in or out of warranty, including models with failed backlights. "
Which, in my opinion, says it all, right there. Of all the manufacturers I know, Samsung is the most dedicated to customer service; not only do they produce excellent products, but they will, flat-out, repair their TVs regardless of warranty. They REALLY want you to keep being their customer.
Contrast this with Panasonic: " In addition, we do occasionally run across a unit that just won't stay fixed or stumps our technical people as to the cause of the defect. … This is not a common occurrence, but when that happens, we will offer to replace the unit at a discounted price. "
Insignia: " Customers who bring in their products outside the warranty period will be assessed a repair cost based on the severity of the issue and the product parts that are available. "
Vizio: " Vizio replaced defective in-warranty sets with refurbished units which, in certain cases, also failed after their warranty period, according to a number of owners. "
So I guess what I'm getting at is that it's not just the quality of the product, or its price, that matters, but whether a manufacturer will stand behind its products.
Samsung does so.
I hope this has given you guys a bit more in your arsenal to deal with holiday shopping - and a few tools to use to brush off salespeople who are trying to baffle you with boatloads of lies, just to get a bigger sale.
