TV Specs – Lies, All Lies?

Posted by: David Birch-Jones at 5:05 pm, June 2nd, 2010

Typical TV Default Settings Are Off the Mark

As I write this blog, my recent review of the JVC Teledock LCD TV for the The Perfect Vision is still fresh in my mind. My experience with the JVC set wasn’t at all unusual and the set performed pretty much as expected, which is to say that it performed pretty poorly straight out of the box (though its performance can be greatly improved if you apply the Recommended Settings that I suggest in the review). The problem, to state things simply, is that the standard or default settings for many TV sets fail to produce accurate, natural-looking pictures.

Even with sets that provide a choice between Dealer (or Demo) mode and Home mode, the Home mode includes various default adjustment settings that are intended to result in a picture that will impress the neophyte, not a video aficionado (or anyone else who appreciates truly accurate picture quality). And, given that Americans collectively bought over thirty million flat panel HDTVs last year, having manufacturers make the assumption that the typical TV buyer is a neophyte and not an informed enthusiast is entirely reasonable.

Specs Gone Wrong: Viewing Angle

Two oft-quoted specs that are virtually always misrepresented are viewing angle and contrast. The first, viewing angle, appeared on spec sheets when the earliest generations of LCD flat panels became available. Now, virtually any LCD-based flat panel HDTV has a viewing angle specification, which is almost always 178 degrees, two degrees short of a complete hemispherical circle. If you think about this for a moment, you’ll realize this is ridiculous, to say the least, since it implies that you can be off almost completely to the side of the screen and still see some sort of watchable picture. Which, if you’re that far off-axis from dead center, is utterly impossible. At 89 degrees off-axis, the most you could possibly see would be a bare sliver of light, with no discernable picture information whatsoever.

When I ask manufacturers why they persist on quoting such a ridiculous specification, they shrug and point out that everyone does it, so they must do so too. Of course, there’s no specific standard for off-axis resolution, which doesn’t help matters either. And the big joke here is that with LCD-based displays, there’s actually a noticeable drop in contrast when you look at the screen from off-axis. In fact, this is one area where plasma technology is king, as a plasma image viewed from far off-axis looks the same contrast-wise as when viewed from dead on-center.

Specs Gone Wrong: Contrast

The other most abused spec in video is the ever-popular (but often meaningless) contrast specification. Back in the days when cathode ray tube was the only video display technology, manufacturers usually quoted ANSI contrast, which is an actual measurement standard, backed up with a defined testing protocol. That standard mandates the use of a checkerboard test pattern (100% white and pure black squares alternating across the screen). The test was developed to determine a display’s “in-picture” contrast, and was especially stressful on a CRT display’s power supply. Sets with a weak power supply would perform poorly compared to a set with a strong and stable power supply, among other variables.

Dynamic Contrast: What’s Wrong With This Picture?

These days, with the exception of some professional broadcast monitors, the contrast specification for most HDTVs and projectors is almost always quoted as “dynamic contrast,” which is full white compared against full black (alternating screens, not via alternating squares on-screen at the same time as it is with the ANSI contrast spec). There’s no official dynamic contrast measurement method either, so comparing contrast ratio numbers from one manufacturer’s TV to another’s isn’t at all useful.

With the advent of LED edgelighting in the latest generation of LCD HDTVs, it’s now possible to have a completely dark picture, with virtually no light emanating from the screen with a pure black video signal. That opens the door to some pretty outrageous contrast ratio specs, with some setmakers now quoting dynamic contrast ratios in the millions to one, compared to conventional LCD in the tens of thousands or thousands to one, and way far above what a well-designed CRT display was able to achieve, which was in the low to mid hundreds to one, as measured using the ANSI standard metrology.

Do You Watch TV in a Dungeon?

In the home however, it’s simply not possible to realize anything like these high contrast ratios, as the room would have to be dungeon-like, with no ambient lighting whatsoever, and with all black walls, floor, ceiling and furnishings—completely light-tight and all surfaces light absorbing and non-reflective. In fact, the room would have to be so dark, that if you held out your hand in front of your face with the lights off, you shouldn’t be able to see it.