How Room Decor Can Corrupt Or Enhance A Perfect Display Calibration

GeorgeAB · 05-17-2007, 10:07 AM

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 #166: "Critical Viewing Conditions For Evaluation Of Color Television Pictures." This is the work from which 6500K 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 and/or 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/ (enter the "lab," click the "Illusions" button and note particularly the "Brightness" demonstrations.)

Professional monitor environments, where critical image analysis is conducted for mastering video programs, use tightly controlled lighting and neutral 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 really are.

Human visual perception is seldom sufficiently understood when consumer, and even many professional, display systems are designed and implemented. Since our human vision is so adaptive, we can think we perceive a "natural looking" image but actually do not 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 the theory alone or decades of imaging industry professional practice.

If you think there is some trick being used in the online images, try printing out the 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 the 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. No calibration instrument can measure this function of the brain.

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

"Advancing the art and science of electronic imaging"

GeorgeAB · 05-18-2007, 03:43 PM

Oops! Sorry about the defective illusions link in the post above. I've repaired it.

GeorgeAB · 05-20-2007, 10:04 AM

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://www.smpte.org/standards/NumberIndex_3_07.pdf .

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: http://cinemaquestinc.com/isf-mag.htm . This special edition 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 video displays.

Kevin C Brown · 05-21-2007, 07:39 PM

George- I haven't looked at the links yet, but I read what you wrote, and theoretically, I understand what you're saying.

But.

If the room is illuminated properly, then does the surrounding color of "stuff" matter that much?

(OK, I just answered my own question, because that illumination, even as low as it should be, still has to bounce off what's in the room!)

GeorgeAB · 05-23-2007, 11:22 AM

Kevin,

Go to the links and examine the demonstrations. You will be amazed and convinced beyond any doubt how important room conditions are to reference imaging.

You will also see how fallacious the statement can be that many make in these forums, "My best judge of color accuracy is my eyes." Our eyes can be fooled very easily and adapt quite readily to changing conditions. Without an objective technical reference, such as a truly neutral color sample, D65 illumination, and/or NIST traceable color analysis instrumentation, our visual perception is unreliable as a calibration tool.

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Brian D H · 05-23-2007, 12:05 PM

Quote:

Originally Posted by GeorgeAB

Without an objective technical reference, such as a truly neutral color sample, D65 illumination, and/or NIST traceable color analysis instrumentation, our visual perception is unreliable as a calibration tool.

Absolutely true, but not 100% useful. Unless my viewing conditions are perfect (and they aren't).

I want my whites to LOOK 100% white and my blacks to LOOK 100% black - likewise red should be red, blue should be blue, etc. It doesn't matter to me if they aren't truely the colors they are supposed to be as long as they LOOK that way to me given my viewing conditions. That having been said I will always want correct calibration as a good starting point - but knowing that my eye is going to effected by other colors in the area I can't be afraid to tweak it later to make it "look" correct. Until I get a perfectly neutral colored home theater (black), I'm going to have to tweak it off of "perfect" calibration. The illusions you posted at the top of this thread prove that.

GeorgeAB · 05-23-2007, 01:08 PM

"I want my whites to LOOK 100% white"

Which color of white are you referring to?

"It doesn't matter to me if they aren't truely the colors they are supposed to be as long as they LOOK that way to me given my viewing conditions."

You have no clue what the colors are supposed to look like in a program, unless you are the program's producer, or have reference viewing conditions. Image fidelity is simply faithfulness to the appearance of the original program.

The only way to insure correct perception of the original program is to follow the same rules adhered to by the program producer. Critical program content decisions in post production are made with a calibrated monitor, in a neutral viewing environment (Gray to white- not black. Black would be useful for a front projection environment, which is not typically used in post production), illuminated with D65 lighting.

You're not fully comprehending a major principle. Our human visual system is adaptive. Without an objective reference, you won't recognize what's accurate. You can only guess.

Guessing is good enough for most video consumers. Most consumers don't have their TV calibrated. They also don't care that much about artistic integrity or value image fidelity. As long as the image vaguely resembles what they consider "reality," it's good enough for them. If it "looks good" to them, then it's good enough for them.

Image fidelity is only preserved when we follow the rules established by imaging industry standards bodies. Display design and calibration must follow the rules. Display environments also must follow the rules or the perception of the image will be skewed. That's what the demonstrations above illustrate. If you think you can accurately compensate for distorted color perception by some intuitive re-adjustment of the display settings, you are mistaken.

Ennsio · 05-23-2007, 03:22 PM

So if there is a window above and behind my tv, should the curtain be gray (or something quite close to gray)?

GeorgeAB · 05-23-2007, 05:42 PM

It should be neutral gray to white. A patterned fabric is actually beneficial, as long as all the colors in the pattern are neutral ( black to white through the gray scale).

For a color match, you can use one of the photographer's 18% gray cards, if you can find one at a camera store. Folks have been reporting these on back order, even in Europe. You can get a 10-step Munsell Color Order System matte gray reference book here: http://cinemaquestinc.com/ideal_viewing.htm . The Munsell system is the reference for surface colors SMPTE uses.