TV Specs – Lies, All Lies?

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

Plus, these overly optimistic dynamic contrast ratios obfuscate and do not educate consumers shopping for a TV, as they fail to take into account how the human vision system works. The time necessary for a person’s eyes to adjust from a moderately lit environment to a very darkly lit situation takes about twenty minutes or so. For a person to become accustomed to an extremely dark environment takes about an hour. This is why general aviation pilots who fly at night by visual rules use specially designed flashlights in the cockpit to read charts and other materials. These flashlights output dim red light, not bright white light, as the red light allows for visual acuity at low ambient light levels. Using a conventional bright white flashlight in the cockpit at night would destroy a pilot’s night vision acuity in a second.

Can TV Pictures Be Too Bright For Their Own Good? Yes.

It doesn’t help that almost all LCD flat panel HDTVs have brighter than necessary backlighting systems. The JVC LT-46P510 is a textbook example, with a brightness specification of 450 candelas per square meter (this spec is sometimes referred to as “nits”). That’s pretty bright, as it’s about eight times as bright as the SMPTE standard for brightness in a commercial movie theater. Just for grins, I put the JVC in the default STANDARD picture mode and cranked up the backlight to full toot, and measured the brightness with a 100% white window. The analyzer came back with a reading of 498 cd/M2, about 10% higher than what was spec’d.

What’s worse is that dynamic contrast is often abetted by active picture level manipulation, more often than not called black expansion, where the average picture brightness level is pushed down even lower with dimly lit scenes. Couple that with a wacky gamma curve, and you end up with a display that can provide an impressive contrast ratio spec, but with crappy picture quality where darkly lit scenes are rendered virtually unwatchable.

The bottom line here is that readers ought not to be swayed by supposedly impressive specifications. The dynamic contrast specification is a useless barometer of picture quality, as is the viewing angle spec. Neither will aid a shopper in making a sensible purchase decision, and either or both might well lead consumers astray.