Measuring Black Level… and 5 Other Home Theater Myths
Diogenes is my Hero. He was, as you may recall, the little Greek fellow (circa. 400 BC) who, armed with a lantern, went running around searching for the Truth. Reports vary as to his success, but there is little question that his mission would be doublely difficult today – especially if he was confining his search to Big Box Electronics stores and gathering data according to “Sparky”, the on-duty salesperson. If there were any teeth at all in the “Truth-in-Advertising” laws, our correctional institutions would be overflowing (even more than they are). All we can do is expose the nonsense from time to time and call “Shenanigans” on specific offenders. This month’s column is another modest attempt at the aforementioned whistle-blowing.
The first topic, the one cited in the by-line, is more of a correction to a non-sequitur than a reveal of a nefarious marketing tactic, but it sets up a more important corollary thought, so stay with me.
1. You can’t measure black!
Yup, that’s right. For all the focus on this important image quality parameter, we can’t truly measure it. We measure “Black Level” with light meters. If the face of a display were truly black (absent all light) we couldn’t measure it! We can only measure a screen’s inability to give us a true black. Even then, the “light leakage” on screen has to be above a certain (very small) level before even the best, most expensive, state-of-the-art instrumentation can quantify it. Wordsmithing, you say? …..well maybe, but it gets me to a more important issue.
2. A display with a measured .002 ft-L black level will produce a better C.R. (contrast ratio)
in my Home Theatre than one that measures .004 ft-L”
uh, maybe not. In fact, in my experience installing and calibrating hundreds of theatres, PROBABLY not. Here’s the thing. The very “best black” you are going to achieve with any display in a given environment is the “room black”. We calibrate all displays with something called “Pluge” patterns that allow us to “just barely see” a 2 IRE stripe or 2% of the light output on the way to peak white. Some of the best discs provide a 1% stripe, but the difference is almost academic. The point is your room has a black level “floor” determined by the ambient light leakage from all sources that can “see” the screen, i.e., light leakage from behind curtains that don’t perfectly seal off the windows, a lamp turned on in an adjacent room, the red, yellow, green and blue LEDs on the face of the equipment rack (even though it may be several feet from the screen), and even, yes, viewer’s clothing. A competent product reviewer would never attempt to measure a very low black level wearing a white shirt! In other words, unless you have a pitch black dedicated theatre with a black velour cloth draped over the front of the equipment, you are probably NOT going to take advantage of that ultra-low black level specification on your new display. Truth is, it was probably manifested as an ultra-high C.R specification (based on a very small denominator). Same deal. Ya ain’t gonna get it without “The Perfect Room”. So while I still concur that REAL contrast ratio remains the most important parameter of those normally cited, it shouldn’t be overemphasized if your light environment is like most I’ve seen – less than perfect.
3. Edge Enhancement
I see this term more and more turning up on user menus as though it was a desirable feature. It’s not. It’s an artifact, and ALL artifacts are undesirable! It’s another trick to try to improve “apparent” C.R. It puts things on the screen that weren’t in the source. Turn it off.
4. BD vs. DVD … “I can’t really see much of a difference”.
I (and most of you) have read the hilarious exchanges on the various forums that allege subtle differences in viewing content on Blu-ray versus standard DVD. These folks should either be rushed to the nearest Lens Crafters for emergency care or be made to realize that they may NOT see a huge difference if they are basing their observations on one of the new crop of $99 BD players connected to a $500 LCD panel with a $14 HDMI cable. All things in balance, folks. On a reference system, or even one a cut or two below in quality, the difference between BD and DVD (audio OR video) is larger than the number of mugs on facebook.
5. “Hold on! Don’t buy anything. 4K is coming”.
We are speaking, of course, of 4,096 lines of vertical resolution (Uber-HD), starting to be touted in a few places. Well, so what. Any content that exists in this format, for now and for the next few years, will likely be prohibitively expensive to get to your living room – never mind the four-times-normal Studio paranoia that will have to be overcome. Unless your screen is larger than any interior wall that I have ever seen, the improvement in image quality per incremental dollar spent is simply a bad bet for now. There is so much high quality 1080 available today, if you wait for 4K, you’ll never catch up!
6. Color Space. “We have 130% more colors”
Yeah, I know. I hit this one pretty hard last month, but it remains a huge marketing “distortion”, and therefore deserves another mention under this month’s topic. There is only one correct color space for the vast majority of what we currently watch – High Definition television and Blu-ray movies. It is NOT as wide as it can be. Technically it’s called rec. 709 and it has very specific places for Red, Green and Blue which define the palette upon which everything we watch is drawn. Over-saturation is as offensive to some as bad de-interlacing or blatant motion artifacts. Unless it can be “fixed” with one button on the remote, sets that feature “larger gamut” are worth less than those that don’t.
As long as consumer electronics companies employ marketing departments, we are destined to be bombarded with “questionable” features, specifications and rhetoric. Our only real defense is to read, question and relentlessly seek out the Truth.
Diogenes, where are you when we really need you?
