Reblogged from MaximumPC
Posted 05/18/10 at 06:03:33 PM
by Dr. Raymond Soneira
Take everything you think you know about displays and throw it out the window. It's time for a clinic on what display specs really mean—brace yourself for the alarming truth
Vision is our most amazing and complex sense, so it’s no surprise that display technology is so amazing and complicated. It’s also no surprise that most consumers don’t have a good understanding of how displays function, or the best way to select them, buy them, use them, and adjust them.
Not only are displays getting more complicated and harder to understand, but the competition between manufacturers has gotten so brutal that marketing gimmicks—ploys that exploit the average consumer’s technical ignorance—are playing an increasing role in driving sales. The goal of this article is to point out and explain some of the most important myths, misconceptions, and misunderstandings about display technology. Much of what you’re going to read is like the classic tale of The Emperor’s New Clothes. What you’ve been told about the latest and greatest thing really isn’t there, or better, or meaningful, or even visible.
In the following pages, I’m going to discuss user controls, contrast ratios, pixel response time, and color gamut. These topics comprise just a portion of what a savvy consumer needs to know, so we’ll be addressing other confusing display topics in future issues of the magazine and on MaximumPC.com. But for now, let’s just start our journey with what should be the best question to ask before buying a new display: “What are the most important manufacturer specs to compare?” Unfortunately, the answer is none, because they’re all exaggerated marketing specs rather than objective scientific specs. The only specs that are useful and meaningful are those in reviews that evaluate every display with the same consistent methodology—like the reviews in Maximum PC.
Confusing Users with User Controls
One reason why most consumers don’t understand their monitors and TVs is because some of the most important user controls have misleading and technically incorrect names. No wonder folks can’t figure out how to adjust them. In fact, they misadjust them, and then usually just leave them misadjusted permanently. Here are some highlights—well, lowlights really—of inane user-control engineering.
When Brightness Isn't
On mobile displays with only a single user control, the control labeled “brightness” does in fact actually control the brightness of the image on the screen by increasing or decreasing the backlight intensity. However, on most monitors and TVs, the control labeled “brightness” does not control the brightness. It actually controls the signal-level setting for black on the display, which indirectly has a minor effect on brightness.
Contrast? Not So Much
The control labeled “contrast” has absolutely no effect on image contrast. It actually controls the brightness of the image, by increasing or decreasing the amplitude of the video signal. Monitors and TVs really should have a true contrast control, but the closest you’ll find on some HDTVs is an obscure control labeled “gamma,” and I have yet to see one that works properly. For more information on gamma, see my article on color and gray-scale accuracy here:
www.displaymate.com/ShootOut_Part_2.htm.
Controls of a Bygone Era
Even more shocking, today’s digital monitors and HDTVs still have the same basic user controls that were found in the original analog NTSC color TVs from 1953: brightness, contrast, tint, and sharpness. These controls only made sense for analog signals on the old NTSC television system. Brightness controlled the CRT direct-current bias, contrast controlled the video amplifier gain, tint controlled the phase of the color subcarrier, and sharpness performed analog high-frequency peaking to compensate for the limited video bandwidth of the old vacuum tube amplifiers. Today, none of these controls are necessary for digital signals.
Rotary controls for a mid-century analog CRT. Those Contrast and Brightness controls are legit.
Brightness and contrast controls shouldn’t be there because, for digital video, the black level is fixed at level 16, reference white at 235, and peak white at 255. Similarly, tint and phase have no real meaning for digital signals. Finally, the sharpness control isn’t appropriate for digital displays because in a digital image there’s no transmission degradation—the image is received exactly as it appeared at the source. Sharpening the image involves digitally processing the pixels, which leads to artifacts and noise unless it’s done at resolutions much higher than the final displayed resolution, which, of course, isn’t the case inside your monitor or HDTV.
Controls that Do Worse Than Nothing
Most monitor and HDTV user-menu options are actually unnecessary features added for marketing purposes—gimmicks to suggest the display has unique features that other models lack. Even worse, most of these options actually decrease image and picture quality.
In many cases, it’s not even clear what these sham controls really do. The documentation seldom explains them, and I even know engineers from high-level manufacturers who don’t know what the controls do, either. When I test TVs, I spend an inordinate amount of time using test patterns to figure out what the options and selections really do, and in most cases, turning off the fancy options leads to the best picture quality and accuracy.
Digital on-screen controls for a Samsung Syncmaster 242MP—that really have no business being labeled Contrast and Brightness.
The following is a list of useless (or near-useless) menu options and selections from three HDTVs sold by major brands: Black Corrector, Advanced CE, Clear White, Color Space, Live Color, DRC Mode, DRC Palette, Dynamic Contrast, xvYCC, Color Matrix, RGB Dynamic Range, Black Level, Gamma, White Balance, HDMI Black Level, Fresh Contrast, Fresh Color, Flesh Tone, Eye Care, Digital NR, DNIe, Detail Enhancer, Edge Enhancer, Real Cinema, Cine Motion, Film Mode, Blue Only Mode.
Some of the terms sound impressive, but almost all of this is unnecessary puffery and jargon that confuses not only consumers but the pros, as well.
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