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"