Display Back Lighting
Dear Gary:
Thank you for providing the best consumer home theatre publication in my occasionally not-so-humble private and professional opinions. I must take exception to some points made by Alen Koebel in his “Six Myths Of The High-Definition Age” article, from your recent September 2007 issue. His “Myth #4” struck close to home, since my company is an award-winning world leader in electronic display viewing environment solutions. My company manufactures and distributes technically correct “bias” lighting for video and data monitors.
Mr. Koebel wrote, “Myth #4: A display with a very high-contrast ratio will be fatiguing, perhaps even painful, to watch.” This is far too general a statement. If he had substituted the word “every” instead of “a” display, his point wouldn’t be so misleading. He contradicts himself later by admitting that HDTVs of limited size, when viewed in a darkened room, actually can induce viewing fatigue.
The scientific and medical communities have been aware since the inception of television that eye strain and viewing fatigue are caused by extended periods of viewing electronic displays. They have recognized consistently that brighter displays are particularly irritating, and even more so in a dark room. Mr. Koebel’s assertion that there is “scant scientific evidence to support a claim of reduced viewing fatigue” when back lighting a display in a dark viewing environment, is not the case. My research over the past nine years has found ample references to the value of providing low-level ambient lighting, which does not reflect off the monitor screen, to promote viewing comfort. A simple Google search for “eye strain watching TV” turns up an abundance of references to scientific and medical articles. This has also been a regular topic in industries that have studied human factors in computer monitor use.
I agree with many of the points made in Mr. Koebel’s article and have included them in my own writings. Many technical topics in the imaging industries are misunderstood and misapplied by consumers and professionals alike. It has been my experience, and my customers’, that properly implemented display back lighting helps owners of HDTVs in much larger sizes than the monitors used in SMPTE’s human factors studies. Home theatre enthusiasts have experienced eye strain and viewing fatigue on widescreen displays as large as 70+ inches diagonal, viewed at relatively close seating distances. There is an abundance of comments to this effect throughout AVS Forum, as an example. Many of my customers over the years have mentioned testing their bias light’s effectiveness by ceasing its use for several days. They prefer their darkened room viewing sessions with back lighting, and recommend the technique to their friends.
My interest in bias lighting began as a consumer about 15 years ago. I learned about the technique from Joe Kane’s writings and other articles in your magazine. My professional imaging industry career started 10 years ago. It became apparent to me that no one in my industry was devoting much attention to providing products and solutions to solve viewing environment problems. Bias lighting, or correctly colored back lighting, has helped thousands of professionals and consumers alike achieve better pictures and more viewing comfort, even with larger TVs viewed at wider viewing angles.
The abundant anecdotal testimonies I’ve read over the years indicate that certain viewers are more sensitive to viewing fatigue than others. It appears that brightness and contrast levels, if high enough, can contribute to discomfort in larger displays for many people. My experience has shown that back lighting brighter HDTVs can solve this problem for those viewers. It is by no means a myth that this technique helps relieve eyestrain and viewing fatigue for users of very high-contrast HDTVs.
G. Alan Brown, President, CinemaQuest, Inc.
Contributing Editor Alen Koebel Comments:
The idea that "a" display (meaning any display in general, not one or some particular kind) causes eye fatigue that could even be painful simply because of a high-contrast ratio is the particular belief I challenge, not the general usefulness of bias lighting under certain conditions, which I acknowledge. That specific belief, which I did not manufacture, does not restrict the conditions to "dark surround." But even so, the idea that this will necessarily lead to fatigue and that said fatigue is due to repeated pupillary contraction and relaxation does not appear to be supported by a preponderance of scientific evidence, notwithstanding that Internet searches can’t find every known piece of information on the planet.
Otherwise, I very much doubt Philips would have felt the need to commission a study. Numerous statements of an idea as an unchallenged fact, even by authoritative bodies such as medical organizations, do not make it true. On the timescale of human history, it was not so long ago that those same organizations believed that bloodletting was an effective treatment for disease.
Nor does anecdotal testimony constitute proof, no matter the abundance. The belief that UFOs are alien spacecraft, for example, is "supported" by abundant eyewitness testimony, including abduction experiences, but none of it has been sufficient to prove the assertion. (I may now be inviting backlash from ufologists!)
Editor-In-Chief and Publisher Gary Reber Comments: I agree with Alen on this. I personally have never found bias lighting to be an asset in watching a movie, no matter what the size of the display. But then, I don’t view movies on anything less than a 32-inch wide monitor or up to 10-feet wide.
A graduate student class and professors at the Rensselaer Polytechnical Institute, which awards graduate and doctorate degrees in lighting design, designed the lighting layout for the first Optimum Performance Home® now being constructed at The Sea Ranch in Northern California for Ultimate Home Design® and Widescreen Review magazines. They did not recommend a bias light in any of the home theatres in the home.
Contributing Editor Joe Kane had this to say about this letter: There is a crossover point among light output, percentage of viewing angle, and frame rate that demands a light behind the image. I wouldn’t want to watch a 22-foot wide screen at 15 to 18 foot Lamberts at 50 Hz or below without some sort of back lighting. Most people have situations in their homes where back lighting would be a good idea. In my office the computer monitor runs at 15 foot Lamberts at 60 Hz. It has a backlight. (The monitor goes into blooming at anything higher than 15 foot-Lamberts.)
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