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How Viewing Environment Conditions Can Corrupt Or Enhance Your Calibration- Updated (1 Viewer)

GeorgeAB

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How Viewing Environment Conditions Can Corrupt Or Enhance Your Calibration- Updated

Fundamentally, all of motion imaging technology is based upon human visual perception. The world's most perfect calibration instrument cannot fully duplicate or measure how our brain interprets what our eyes see. Certain attempts have been made to emulate how humans perceive light but science has yet to produce an instrument which tells the whole story.

The Society of Motion Picture and Television Engineers (SMPTE) human factors work resulted in their recommended practices document RP166-1995: "Critical Viewing Conditions For Evaluation Of Color Television Pictures." This is the report from which D65 bias lighting has been derived. The document actually devotes much more attention to color perception than eyestrain.

SMPTE updated this research after 22 years and published a revised standards and recommended practices document, SMPTE ST 2080-3:2017, titled: “Reference Viewing Environment for Evaluation of HDTV Images.” Its introduction reads:

“The creation of television images that are intended to follow a standard of consistency in reproduction requires definition of a reference display, of a controlled viewing environment, and of a set of measurement procedures to enable consistent calibration of both display and environment. This document specifies a controlled viewing environment referred to as the Reference Viewing Environment.”

In other words, video program producers value image fidelity in order for their intended audience to enjoy a faithful reproduction of their workmanship. They adhere to industry standards and best practices to preserve the motion images they produce for display. It is acknowledged that both video monitors and viewing room conditions must be calibrated in order to provide an authentic viewing experience. SMPTE’s research validated that room surface colors and ambient lighting characteristics affect the viewer’s perception of the video display’s image.

Here are some links that dramatically demonstrate how ambient lighting and surrounding surface colors in the room can cause us to think we see black levels, contrast, and/or colors a certain way.



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 interior decorating choices can be.

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 electronic 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 might indicate. 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: CinemaQuest, Inc. .

Best regards and beautiful pictures,
G. Alan Brown, President
CinemaQuest, Inc.
SMPTE, PVA, THX, ISF, Lion AV Consultants

"Advancing the art and science of electronic imaging"
 

Gregg Loewen

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hi Alan. Great information.
Summary, BACKLIGHTS ARE PART OF A REFERENCE ENVIRONMENT FOR BOTH SDR HDR.
SDR bias lighting should be at 10% (or 10 nits), HDR bias lighting should be at 5 nits.
Biaslighting does not apply to projectors.
 

GeorgeAB

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For the technically astute, here is an impressive interview by Murideo (calibration instrument provider) with the developer of the MediaLight line of LED bias lights:
(1:27:17 Video)
The interview offers many great PowerPoint slides of relevant graphs and examples of human perception in this category of light and color.
 
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GeorgeAB

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Need help adjusting the proper level of ambient lighting in your viewing environment? Here are some of the more recent sources for test patterns that allow for visual adjustment of bias light levels:

The best source I'm aware of for 5, 10, and 15 nit (candelas per square meter) patterns with helpful explanations is the "UltraHD|HDR-10 Video Calibration" program from Diversified Video Solutions.

Another popular, less comprehensive source is the "UHD HDR Benchmark" program from Spears & Munsil.

Older HDTV test/calibration programs with usable patterns include those from Video Essentials and Spears & Munsil.
 

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