[Publisher's Note:  The following article is provided to ISF Forum readers by G. Alan Brown, the founder of CinemaQuest Inc. and creator of Ideal-Lume, the sole source for reference standard lighting products used in professional and home viewing environments throughout the world. Alan is one of the world's most knowledgeable, passionate and eloquent advocates for display industry standards and imaging excellence. We're pleased to be able to provide Alan with a platform to explain why your home viewing environment matters and what you can do to make it work better for you.

You can read more about Alan and his background here.]

There’s no doubt about it – consumers are becoming ever more demanding about television picture quality. This relatively new phenomenon is largely being driven by the fact that consumers have begun to move en masse to HDTV. As a result they’re suddenly spending anywhere from three to 10 times (or more) what they would have paid half a decade ago on a box-standard, replacement-level color television.

And, as a result, consumer expectations have been irreversibly raised.

While it appears that even casual viewers understand that HDTV technology is at the heart of the picture quality improvement all those extra TV dollars are delivering, there’s also an apparent realization that while the display may be the biggest and most obvious piece of the picture quality equation, it is most definitely not the only consideration.

This is probably most apparent in the explosion in demand for HDTV programming – whether it be over-the-air broadcasts, cable or satellite program delivery, or via new packaged media, such as Blu-ray and HD DVD discs. There’s also rapidly growing interest by consumers in professional video calibration services, as well as the use of high-end cables and interconnects, video scalers and processors, and power management and conditioning solutions.

All in the quest for even better picture quality.

The Missing Link: The Viewing Environment

Given all that, there’s still one fundamental ingredient in the picture quality recipe that is the least-recognized, the least-understood, and without question, the most consistently overlooked element – the viewing environment. Despite a traditional indifference to viewing environment requirements, they have a direct and weighty impact on the picture quality that an HDTV can deliver to viewers.

Perhaps the best way to bring the mystery of the ideal home viewing environment into clearer focus is to gain an appreciation for the importance these factors are given by film industry and television professionals.

The Society of Motion Picture and Television Engineers (SMPTE) is responsible for setting standards and practices for the motion picture and related industries. The organization’s recommended practices document, “Critical Viewing Conditions for Evaluation of Color Television Pictures,” deals very specifically with viewing room conditions and the interaction of viewers with studio monitors and the environment in which they are used.

SMPTE’s human factors research discovered that viewing conditions can have a profound impact on how viewers perceive video images, and they also revealed key findings in how these factors can also assist or impede viewing comfort. SMPTE’s work applies to all forms of electronic displays, so these recommendations can also be applied in other, similar types of environments, such as desktop computing, digital graphics design, digital photography, electronic interactive games; as well as applications in technical, medical, industrial and security applications where accurate imaging is an important factor.

Professional film and video production environments require complete control over ambient room lighting, and the production facilities make use of neutral colors for walls and ceiling areas near the video monitors. These room characteristics ensure correct color perception and image fidelity.

Providing consistent viewing conditions is particularly important in the very common scenario where a project may stretch on for weeks or months at time, involving a large and changing contingent of professionals working on various aspects of a production.

Following display industry standards ensures quality, consistency, repeatability and fidelity to the director’s artistic vision all through the production and program delivery chain.

All of this is important for the consumer to understand and to recognize, because your home entertainment system effectively stands as the final link in the program production chain.

But apart from the lucky minority who own a dedicated home theater room, replicating all of the various SMPTE standards and practices can present some interesting home and hearth challenges. Still, residential viewing environments can be set up in a way that incorporates or emulates many of the more important professional viewing environment conditions.

The Typical Home Viewing Environment

First let’s take a look at a non-dedicated viewing environment, such as a family room or media room.

• Room Lighting.  First and foremost, room lighting must be controlled to avoid screen reflections. Reflections, haze, and diffused glare will interfere with the light coming from the display and this will result in direct compromises in picture quality.

SMPTE recommends that during viewing, all ambient lighting should be restricted to the area behind the display, so that it illuminates the wall facing the viewer. This method of display backlighting is called “bias lighting,” and in addition to ensuring that light does not fall onto the screen area or in the path from display to viewer, such lighting is beneficial in significantly reducing viewer eye strain.

During the course of the typical movie or TV program, the images that appear on screen range widely from very dark to very brightly lit scenes. This range of picture brightness causes the iris in our eyes to open wide during dark scenes and then shutter down during the brightest images. Over time, this leads to fatigue to our eyes and associated muscle groups, causing short-term discomfort and possibly long-term fatigue.

Correctly implementing bias lighting into the typical home viewing environment will minimize the extremes of iris movement and lead to more comfortable viewing.

• Color of Room Lighting.  Ambient lighting in use during viewing should also be the correct color – in fact, it should be as close as possible to the same color temperature standard as used in display calibration -- D6500 or 6,500 Kelvin, which is said to be roughly equivalent to northern sky daylight.

This color of D6500 light is bluer in spectrum than typical incandescent lighting, which tends to register around 3,200 Kelvin, which falls into the yellow/red area of the spectrum. The most common source for D6500K lighting is full-spectrum fluorescent lamps.

Currently, the sole source for reference-standard, adjustable and pre-assembled bias lighting is www.cinemaquestinc.com.

• Brightness of Ambient Lighting.  SMPTE recommends the level (brightness) of ambient lighting should be no greater than 10% of the brightest white produced in the video image on the display. This level can be achieved through the use of standard test patterns that are included in most home theater setup DVDs, such as “Digital Video Essentials,” produced by Joe Kane Productions.
  

•  Bias Lighting: The Fringe Benefits.  Bias lighting can also enhance the perception of black levels in the image. This is particularly helpful for TVs that have a difficult time producing satisfactory blacks. An effective demonstration of how this works can be found at:

http://www.lottolab.org/

Enter the "lab," click the "Illusions" button and take special note of the "Brightness" demonstrations.

•  Wall & Ceiling Colors.  Room surface colors are also very important to the viewing environment. SMPTE recommends neutral colors for areas surrounding the TV. This preserves correct color perception for the viewer. 

http://www.echalk.co.uk/amusements/OpticalIllusions/illusions.htm

• Seating Arrangements.  Seating locations relative to the screen must be addressed. SMPTE recommends that viewing angles for primary seating be within +/-15 degrees of the centerline of the screen on the horizontal axis. These recommendations also suggest a vertical viewing angle that places the center of the screen 15 degrees below horizon for maximum viewing comfort.

Display viewing angle performance must be taken into account as well. The brightness and color uniformity of the image will diminish with most displays as one moves farther off axis. Plasma displays are superior in this regard, while LCD and many rear-projection screens are susceptible to light falloff and/or color shifts as the viewer moves further off center axis.

• Viewing Distances.  The distance the viewer is from the screen also will have a significant impact on perceived image quality.
  

Standard definition (480i) images look best at a minimum distance of 6 screen heights. To explain the concept of “screen heights,” if your widescreen television has a diagonal screen size of 50 inches, the height of the screen is roughly 24 inches, which for standard-definition images would translate to an optimal viewing distance of 12 feet (24 inches x 6 = 144 inches, or 12 feet). Progressive DVD programming (480p) can be viewed a bit closer.

• Visual Distractions.  Room elements should not cause distractions while viewing is in progress. Of particular concern are reflective objects that light up as changes occur in image brightness on the screen. Moving objects, like clock pendulums, etc., should not be within the field of view with the screen.
  

Lights and displays from electronic components are best covered by cabinet doors or located remote from the field of view.

• Display Surround Distance.  SMPTE also recommends that displays be located away from the wall behind it to aid viewing comfort during extended viewing sessions. The organization specifies a minimum distance of 2 ½ times the screen height. In general, this is impractical for many viewing environments, especially with the current preference for wall mounting of flat-panel displays.
  

Dedicated Home Theaters

For true home theater room applications, all of the previously discussed principles should be considered. But of those, the most critical are room lighting and surface colors.

• One Light Source = The Projector.  The only light that should reach the screen is that from the projector. Ambient light sources should be absent. Room surfaces should be dark and absorptive or non-reflective. A flat-finish black ceiling is strongly recommended. Any extraneous light that hits the screen or is reflected back onto it will impair black levels, contrast and color fidelity, and these reflections are made worse by vivid, non-neutral colors in the room decor.
  

• Not Too Bright.  Screen brightness can be overdone. An image that is too bright may cause eyestrain during extended viewing sessions and in the extreme would require screen backlighting, which is very difficult to implement without light reflecting back onto the screen. High-gain projection screens may be helpful with projectors that lack sufficient light output, but these screens come with other compromises, including uneven light distribution (“hot spots”) and color shifts.

•  Rear, Middle & Front.  The Imaging Science Foundation suggests providing three rows of chairs in multi-seat theaters. The first row would be used for high-definition viewing, the middle row for standard-definition DVD and the back row for NTSC standard-definition programs.

Bear in mind that these principles represent the recommendations for an ideal viewing environment. Non-dedicated, multi-purpose viewing environments often require various types of compromises to these ideal conditions. Simply keep in mind that the closer you can come to these imaging recommendations the better, and the more you deviate, the greater the compromises in image fidelity and viewing comfort will be. 

For the viewer who values artistic integrity and image fidelity most, it’s all about the art.

 Copyright CinemaQuest, Inc. © 2007

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