How Viewing Environment Conditions Can Corrupt Or Enhance Your Calibration

The world's most perfect calibration instrument cannot measure how our brain interprets what our eyes see. Some attempts have been made to emulate how humans perceive light but science has yet to produce an instrument which tells the whole story.

SMPTE's human factors work resulted in their Recommended Practices document RP166-1995: "Critical Viewing Conditions For Evaluation Of Color Television Pictures." This is the work from which D65 bias lighting is taken. The document actually devotes much more attention to color perception than eyestrain. Here are some links that dramatically demonstrate how ambient lighting and surrounding surface colors in the room can cause us to think we see better black levels, enhanced contrast, and/or perceive distorted colors that aren't really in the image.

http://www.echalk.co.uk/amusements/O.../illusions.htm (Note particularly the "Colour perception" and "Colour perception 2" demonstrations.)

http://www.lottolab.org/articles/illusionsoflight.asp (Note particularly the "Brightness illusions" and "Colour illusions")

Professional monitor environments (where critical image analysis is conducted for mastering video programs) use tightly controlled lighting and neutral colored surfaces surrounding the display. The demonstrations above make very clear the importance of incorporating similar room conditions, if image fidelity is desired. This material also makes abundantly clear how destructive to image fidelity the Philips 'Ambilight' colored light features and similar gimmicky fads really are.

Human visual perception is seldom sufficiently understood when consumer display systems (and even many professional ones) are designed and implemented. Since our human vision is so adaptive, we can think we perceive a "natural looking" image but actually don't, if viewing environment conditions are incorrect. The demonstration material at the links above should provide considerable practical reinforcement for folks who have a hard time being persuaded by imaging science theory alone, or even the decades of proven imaging industry professional practice.

If you think there is some trick being used in the online images, try printing out the colored demonstration patterns and making your own paper masks. You will see that the only "trick" involved is being provided by your own brain. This is why even a perfectly aligned display device can indeed look different than a calibration report says. Conflicting viewing environment conditions, such as the wrong lighting or colored room surfaces within the observer's field of view, will ALWAYS distort how a video image appears to the viewer. No calibration instrument can measure this function of the brain. It's simply a perceptual issue.

If a consumer cares about achieving the same "look" of a video program in their home that the mastering technician enjoyed, calibrate the display, and emulate the viewing environment conditions professionals consider best practices. I like to think of this extra effort as fidelity insurance.

Here's a white paper discussing these issues and how they can be incorporated into designing good viewing systems: http://www.cinemaquestinc.com/ive.htm .

Best regards and beautiful pictures,
G. Alan Brown, President
CinemaQuest, Inc.
A Lion AV Consultants Affiliate

"Advancing the art and science of electronic imaging"

Angryht,


I don't think you're "guessing," but instead arriving at a logical conclusion, founded upon your understanding of simple imaging science principles. However, front projection environments have unique characteristics, different from free standing and direct view type displays. Dark, nearly neutral colors can be OK for front projection theaters. Vivid colors should be avoided, except as minimal accents. It's essential to keep in mind that light can bounce back to the screen from room surfaces, thereby contaminating the image being projected.

It's also important to understand that what is "more appropriate" depends upon your design goals for the system. This section of the forum is dedicated to display calibration. I'm inclined to assume that anyone reading this section is primarily interested in image fidelity and display accuracy. To achieve those interests requires that we follow certain rules, the same rules followed by program producers.

Motion imaging industry standards organizations, such as SMPTE, set the rules. Compromises must be weighed against design priorities. If image fidelity is the top priority, room decor must follow imaging science, rather than aesthetic preference. Providing a flat black ceiling in a front projection theater is a good example. Black ceilings are usually not a hot item to interior decorators.


You're right, a lot of people do. A lot of people are oblivious to the term 'image fidelity,' including some system designers. Such people have every right to use whatever design priorities they consider "more appropriate" for their lifestyle and how they plan to use the room. Many homeowners want to show off the room with all the lights on more than they want image fidelity when the display is used. Such consumers typically don't take an interest in display calibration.

If image fidelity is most important, don't base your plans for a dedicated theater design upon magazine photos or anyone's opinion. The foundation of reference display system design must be imaging science. Award winning home theaters are usually judged by how the room looks in photographs, with all the lights on, rather than how the system performs. Be clear about your priorities, keeping in mind that any element in the system design which diminishes picture and sound fidelity reduces the value realized from the equipment, the programming purchased, and the time devoted to their use.

Image fidelity has nothing to do with pleasing the audience's eyes and everything to do with preserving what pleased the program producer's eyes. It's all about the art. The consequences of a white ceiling in a front projection theater include compromised contrast and diminished color saturation.

People have been inquiring about where to get the SMPTE RP166-1995 document mentioned above. This technical reference is available from the Society Motion Picture and Television Engineers directly at: http://store.smpte.org/product-p/rp%20166-1995.htm .

Half the cost can be saved by getting the Widescreen Review back issue of their special edition titled, 'Imaging Science Theatre 2000' from 1998, which includes a reprint of the document,with SMPTE's permission: http://cinemaquestinc.com/isf-mag.htm . This special edition of around 400 pages also includes much more detail about display viewing environment conditions and imaging science principles. It should be in the library of anyone serious about ultimate video quality and display standards.

Don't be too hard on your friend. We all have narrow and broad mindedness, just on different subjects. Each of us are entitled to our own set of priorities and preferences. I constantly endeavor to guard against dogmatism. Image fidelity is simply not a top priority for many people. My intent is to educate and confront wrong information, misunderstanding, and confusing industry practice, by using reference standards, imaging science, logic and reason.

We all come from the factory with differing aptitudes, preferences, inclinations and talents. Some people will never be persuaded, even by demostrations and logic. They just don't 'get it' and never will. Concentrate on those who express an interest in what you have to offer. Your capacity for persuasion has limits, and those limits are often times totally outside your control.

Best regards and beautiful pictures,
G. Alan Brown, President
CinemaQuest, Inc.

"Advancing the art and science of electronic imaging"

Many folks are put off by the thought that their room could end up looking like a battleship, with medium gray walls. For self-contained video displays, only the area surrounding the TV (within your field of view while watching the screen) needs to be neutral colored. White is also neutral. Neutral colored patterns, wall hangings, and/or textures can be incorporated to add interest.

The wall opposite the TV does not have to be gray either. SMPTE's recommendations also allow for nearly-neutral colors to be used elsewhere in the room.

Black is usually very neutral. I personally find the high gloss black frames a distraction, since they act like mirrors. The early digital TVs had silver or gray frames and cabinets to call less attention to the poor black levels on the screen. This has improved over the years and manufacturers are more confident about surrounding the image with a black border. If I had a gloss black frame I would cover it with black Duvetyne tape.

The National Institute for Standards and Technology (NIST) has labs near me in Boulder, CO. They have assigned one of their physicists to evaluate methods to help professionals and consumers select the right flat panel display for a given application. One very big factor that was considered is the impact the display's environment has upon the picture. NIST provides a nifty tutorial on their web site to illustrate how different flat panel display types handle various viewing environment challenges. Here's the link to the tutorial: http://www.fpdl.nist.gov/tips.html . It features a PDF slide show that you can save in a file. Many of the images are very good examples of the kinds of interferance to picture quality that poor viewing conditions can present.

Here's a link to a recent article in the Rocky Mountain News featuring an interview with the man who runs this department at NIST's Boulder labs: http://www.rockymountainnews.com/drm...558486,00.html . This newspaper article will only be available for a limited time.

The newspaper article link above was defective. I have repaired it. Sorry!

Here's another reference for calibrators and hobbyists interested in professional documentation of international standards for display viewing environment theory and practice.

ITU-R BT.710-4 "Subjective Assessment Methods For Image Quality In High-Definition Television,"

To order via Word document or PDF download: http://www.itu.int/rec/R-REC-BT.710-4-199811-I/en

Best regards and beautiful pictures,
Alan Brown, President
CinemaQuest, Inc.

"Advancing the art and science of electronic imaging"

Here's a recent article that looks at the effects of ambient lighting upon color perception and contrast in flat panel TV environments: 'Illumination and Displays: Color Appearance of a Display Changes Under Various Illumination Conditions'

http://spie.org/x13920.xml?highlight=x2408

The article is from SPIE: an international society advancing an interdisciplinary approach to the science and application of light (formerly: The International Society for Optical Engineering). There are plenty of interesting links on their web site for more data on electronic display viewing environments and human visual perception.

Here's a neat trick for folks who balk at the bat cave concept. Use darker shades of gray, rather than black, especially on the front and side walls. Illuminate the neutral gray portions with soffited or baffled colored lights. The lights will turn the gray portions of the room any color you want. This gives unlimited color choices for the designer to use when the lights are on in the room. Darker shades of gray are very nearly as effective as flat black during the showing of the movie.

More colored light options are appearing on a regular basis with LED arrays. In fact, the red/green/blue arrays can be controlled electronically to produce just about any color in the spectrum. Conventional white lights can be added for times when the room must be navigated in or for cleaning.

The LED arrays would offer automated color schemes that could be changed with mood or theme. How about green, prior to showing 'The Matrix' films. Blue could be used prior to 'The Terminator.' Red would be appropriate prior to a Dracula flick. The options are only limited to the owner's imagination.

Best regards and beautiful pictures,
G. Alan Brown, President
CinemaQuest, Inc.

"Advancing the art and science of electronic imaging"

I expect one foot is still sufficient to provide the intended benefits. This may limit the benefit at wide horizontal viewing angles for other seating locations (depends on whether the TV cabinet is very deep).

Here are two linked articles discussing display viewing environment principles at the new public ISF Forum site:
http://www.isfforum.com/FAQs/view/IS...ortant/33.html
http://www.isfforum.com/index.php?op...d=51&Itemid=48

Best regards and beautiful pictures,
G. Alan Brown, President
CinemaQuest, Inc.

"Advancing the art and science of electronic imaging"

The second link listed above is temporarily non-functional due to some updates and edits being done by the isfforum.com admin. I'll let this thread know when the article link is working again.
Here's a temporary replacement for that link: http://cinemaquestinc.com/ive.htm . It's a white paper with the same info, just more technical in format.

The link in post 26 has been repaired.