High Definition. In the world of home video this format has become the gold standard. So it’s no surprise that many display products in the market (flat screens, computer monitors, projectors) claim to be HD-compatible. But are all HD displays created equal? It’s all in the specs…
When shopping around for a new TV, monitor or pojector, you’re going to be considering a number of factors: How good does the image look? How big should the image be considering the size of the room? Do you want plasma, LCD, rear or front-projection? All are worthwhile questions. But there’s something else you should be asking while doing your research: Is this unit simply capable of displaying a HDTV signal, or will it display it the way it was meant to be displayed?
To the unititiated, that’s a bizarre question – either a display is HDTV compatible or it isn’t right? The answer lies somewhere in the middle and it hinges on one particular specification: resolution.
In the world of HDTV, there are three standards (currently). 720p, 1080i and 1080p. The numbers refers to the amount of vertical lines of resolution in the signal, whereas the letter indicates how the image is displayed (i for interlaced, p for progressive). For now, we’re going to cover what the numbers mean and leave the letters for another posting.
In order for a TV or other display to show you all of the detail in a HDTV signal, it needs to meet a minimum standard in terms of vertical resolution. Display resolutions are always quoted in a HxV format where H is the horizontal resolution and V is the vertical resolution – remember your old math class rules? The horizontal value on a graph always comes before the vertical value :-)
So if a display has a quoted resolution of 1366×768, that means it can display up to 768 lines of vertical resolution. That also means it can handle every detail present in a HDTV signal in the 720p format. In a strangely unintuitive way, it can also handle 1080i, but let’s stick to the 720p example for now.
Okay, so you’re looking at a display and it claims to be "fully HDTV compatible", but it only has a quoted resolution of 800×600 (this is more common among projectors than flat planels). Is the manufacturer lying? No. Well, they’re just not telling you everything.
If a display doesn’t meet the resolution requirements of a 720p HDTV signal but still claims to be HD compatible, it means that the manufacturer has equipped the display with some very clever software which performs an operation known as "scaling". Scaling allows a display of lower resolution to still show you a HDTV movie, or TV program – it just won’t be able to show it to you with all of the detail that a higher resolution display is capable of.
This is the main difference between older TV’s that can only display standard TV signals (480i) and lower-than-full-HD-resolution displays – your old TV can’t show you HDTV at all.
Now that you know what to look for in resolution in order to see a true HDTV picture, the question becomes: do you care? For some folks, the lower price of a lower-than-full-HDTV resolution display is justification enough. If you’re primarily in the market for a projector that will let you see your computer’s screen content at a much larger size, then perhaps this compromise is perfectly acceptable. According to some studies, resolution is the least important of a series of 4 specifications that make HDTV viewing the experience that it is (in order: Contrast Ratio, Colour Saturation and Colour Accuracy).
Want to dig a little deeper on this whole resolution issue? Check out this excellent primer from CNET’s David Katzmaier