Understanding HDTV Resolutions

A Tale of TVs

By Bryan Lambert

With February 17, 2009 looming and prices for flat panel televisions falling, even in these hard economic times, people are still looking to purchase an HDTV either by choice or by necessity. When looking at High Definition televisions you may have heard about the 720 and 1080 standards, but sometimes there is a bewildering amount of information to take in when choosing “just the right” television for your needs. Let’s look at some things to look at when purchasinga HDTV, particularly at what is called “the glass.”

 

The Glass and an Account of Resolutions

In the computer parts or consumer electronics industry, it all starts with the “glass” – this is the name that the LCD or Plasma panel is commonly called – this is the heart of the HDTV. In this Tech Tip, we’ll concentrate more on different aspects of the glass (which for simplicity sake, I’ll refer to as the “panel”), particularly the resolution.
The quality and the resolution of the panel used makes up a large part of the quality of the picture that ends up on the television. One thing you may notice very quickly is, no matter the size of the television, that a very common panel used for HDTVs has a resolution of 1366 x 768 pixels. Unfortunately, the two most common HDTV resolutions are 720 (1280 x 720 pixels) and 1080 (1920 x 1080 pixels). It doesn’t take a math major to see that 1366 x 768 doesn’t quite “fit” into either 1280 x 720 or 1920 x 1080.

Another thing that you may see is that many HDTVs that use a 1366 x 768 pixel panel are often advertised as 720p/1080i televisions. Why is that? Well, usually, these televisions will accept a 720p signal and scale it up to a 1366 x 768 resolution or a 1080i signal and scale it down to a 1366 x 768 resolution. Is this a bad thing? Not really. The reason is that most scaling chips work very well, and the resulting picture is usually pretty good. If the television is getting a 1080i signal, it will actually get more information than it can use, but the resulting picture will be very much on par with a 720p signal – and truthfully many people cannot really differentiate between the two.

Now, a quick note about those lower case letters after the resolution. The lower case i simply stands for “interlaced” and p for “progressive”. This has more to do with the type of high-definition signal coming into the TV rather then the actual playback (HDTV panels do not play back in interlaced mode, like old style analog televisions, just in progressive scan).

Full High Definition – it’s alive, IT’S ALIVE!

A panel that is a true 1080 resolution (1920 x 1080 pixels – usually advertised as 1080p) will usually provide a better picture then a television with a 1366 x 768 panel since it is a true pixel to pixel representation of the information coming into the television. Currently, only high resolution products such as Blu-Ray players or the now defunct HD-DVD players could take advantage of 1080 resolutions in “progressive scan” mode (1080p), as television stations do not currently broadcast HDTV 1080p signals. To differentiate televisions with this higher resolution capability, many manufacturers advertise these televisions as “Full HD” or “Complete HD.” A 1080p television using a 1920 x 1080 panel will usually look better than a similarly sized television using a 1366 x 768 panel (really any panel size under the 1920 x 1080 resolution.)
The question may arise: “why is there a wide price disparity in 1080p televisions?” A lot has to do with such things as contrast ratio(expressed as x:1, the larger the x is, the better the contrast ratio) and brightness of the panel (expressed as x cd/m², the larger x is, the better – note that this spec is usually not included), how fast it refreshes (expressed in milliseconds, usually x ms – the lower x is, the better), what kind of television tuners are included (none, analog, digital, etc), the “electronics” surrounding the panel, what kind of features/connectors are offered (such as HDMI), if any extras are built in (speakers, DVD player) and whose name is on front of the TV.
For many, really the best way to shop for a HDTV is to see the picture in person. If you’re buying a television without seeing it in person, then you may want to rely on the listed specifications of the television as well as product reviews so that you can make an informed decision (some good sites for reviews are CNet (http://reviews.cnet.com), HD Guru (http://www.hdguru.com/), and of course, the ever popular Amazon (http://www.amazon.com). 

Yes, There’s Lots More – But Not Today

Once you scratch the surface on HDTVs you find out there is a lot to learn – much more than could be crammed into just one Tech Tip. In fact, there is almost a confusing over-abundance of HDTV information available! So, if you do find yourself looking for an HD television, stick to the basics: does the picture look good; does it fulfill my needs; is it within my budget? However, always remember: it all starts with the glass.