White monitor calibration - AVS Forum
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post #1 of 5 Old 08-09-2013, 05:57 AM - Thread Starter
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Hello to all, I am new in the forum and my question this is:
in the monitor with white point correctly calibrated, the white must appear pure white at dark room ? or blue for D65 white point and yellow for d50 white point ?
What color should appear this:
Created with GIMP
Thanks
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post #2 of 5 Old 08-09-2013, 08:45 AM
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Quote:
Originally Posted by avse View Post

Hello to all, I am new in the forum and my question this is:
in the monitor with white point correctly calibrated, the white must appear pure white at dark room ? or blue for D65 white point and yellow for d50 white point ?
What color should appear this:
Created with GIMP
Thanks

A large range of colors will appear pure white in a darkened room. Your eye is extremely adaptive to the brightest color, so D93 all the way through D50 would all appear to be untinted white without another bright known color to reference.

The image you posted is RGB 255,255,255. RGB is a relative color space, RGB can encode AdobeRGB, sRGB or any number of colorspaces. The default colorspace for content on the internet is sRGB that specifies that 255,255,255 represents D65.

Joel Barsotti
SpectraCal
CalMAN Lead Developer
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post #3 of 5 Old 08-09-2013, 09:42 AM
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Just to dumb-down his answer a little:

For any device you'd (realistically) be watching a movie on in the dark the answer you're looking for is D65.
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post #4 of 5 Old 08-09-2013, 09:47 AM
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Quote:
Originally Posted by sotti View Post

Quote:
Originally Posted by avse View Post

Hello to all, I am new in the forum and my question this is:
in the monitor with white point correctly calibrated, the white must appear pure white at dark room ? or blue for D65 white point and yellow for d50 white point ?
What color should appear this:
Created with GIMP
Thanks

A large range of colors will appear pure white in a darkened room. Your eye is extremely adaptive to the brightest color, so D93 all the way through D50 would all appear to be untinted white without another bright known color to reference.

"Monitor white reference: In additive mixture, the illumination of the reproduced image is generated entirely by the display device. In particular, reproduced white is determined by the characteristics of the display, and is not dependent on the environment in which the display is viewed. In a completely dark viewing environment, such as a cinema theater, this is desirable; a wide range of chromaticities is accepted as “white.” However, in an environment where the viewer’s field of view encompasses objects other than the display, the viewer’s notion of “white” is likely to be influenced or even dominated by what he or she perceives as “white” in the ambient. To avoid subjective mismatches, the chromaticity of white reproduced by the display and the chromaticity of white in the ambient should be reasonably close." from Charles A. Poynton's, 'Digital Video and HDTV Algorithms and Interfaces'

A vital and fundamental key to understanding how electronic imaging works is to have a foundational knowledge of the human visual system. Human factors cannot be divorced from display system design/performance/calibration. Confusion, misapplication, and misinformation in the discussion of display performance are frequently due to a poor understanding of how vision works. Any formal course in video technology worth its salt will begin with the study of the human visual system. The phenomenon of adaptation in human perception- what it is and how it works- is a fascinating study that is essential for correctly applying video technology.

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

"Advancing the art and science of electronic imaging"
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post #5 of 5 Old 08-10-2013, 08:17 AM
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Quote:
Originally Posted by GeorgeAB View Post

"To avoid subjective mismatches, the chromaticity of white reproduced by the display and the chromaticity of white in the ambient should be reasonably close."

Based on that I decided once that I'd be better off just to put some gray bars on the display and adjust them by eye until they looked white to me (for daytime).

The light in the room was basically cyan (mostly green) because of some window tinting, and sure enough I found I had to really crank the green and cut the red before it appeared white to me subjectively.

The picture actually looked good that way, I'd say the experiment worked. (But I put it back because on that set I could only customize one mode and didn't care to use that at night).
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