Hi,zur Praxis der grauen Leinwände vs. weisse Leinwände :
chessbase.com/puzzle/puzz10b.htm

Ein Ausschnitt -

"...Can you believe that the squares marked A and B in the above picture have exactly the same?

If you use a pipette to examine the squares you will see that both are exactly the same shade of grey (RGB = 107, 107, 107)

Once again closer scrutiny does not help. Or are you able to convince yourself that an identical shade of grey was used in the picture on the right?..."

Hi,mein Grund für diesen Link waren meine Vergleichstests weisser/grauer Leinwand.
Mir fiel auf das der "gefühlte" Bildunterschied viel höher war,als die physikalischen Grundlagen es erlauben sollten.
Also suchte ich nach einem Grund für die Differenz zwischen dem Wissen und dem was das Auge/Hirn wahrnimmt.
Dieser Link enthält meiner Meinung nach eine Erklärung für diese Graue-Leinwand-Phänomen.



"...A description of the illusion is given at Prof. Adelson's web site. Essentially it says that our visual system does not simply measure the light coming from a surface, but interprets the luminance in the context of its surroundings. The brain knows that a light surface in a shadow may reflect less light than a dark surface in full light. Adelson explains how the brain determines where the shadows are and how to compensate for them in order to determine the shade of gray that belongs to the surface.

"The first trick is based on local contrast. In shadow or not, a check that is lighter than its neighboring checks is probably lighter than average, and vice versa. In the figure, the light check in shadow is surrounded by darker checks. Thus, even though the check is physically dark, it is light when compared to its neighbors. The dark checks outside the shadow, conversely, are surrounded by lighter checks, so they look dark by comparison.

A second trick is based on the fact that shadows often have soft edges, while paint boundaries (like the checks) often have sharp edges. The visual system tends to ignore gradual changes in light level, so that it can determine the color of the surfaces without being misled by shadows."

It is important to note that none of the above is a defect in our visual system, but rather a very sophisticated system that process the data that it receives. "The visual system is not very good at being a physical light meter, but that is not its purpose. The important task is to break the image information down into meaningful components, and thereby perceive the nature of the objects in view."...

Hi,der Grund für meinen Thread habe ich in meinem letzten Beitrag versucht zu erklären.
"...mein Grund für diesen Link waren meine Vergleichstests weisser/grauer Leinwand.
Mir fiel auf das der "gefühlte" Bildunterschied viel höher war,als die physikalischen Grundlagen es erlauben sollten.
Also suchte ich nach einem Grund für die Differenz zwischen dem Wissen und dem was das Auge/Hirn wahrnimmt..."

"... Essentially it says that our visual system does not simply measure the light coming from a surface, but interprets the luminance in the context of its surroundings..."
"The visual system is not very good at being a physical light meter, but that is not its purpose. The important task is to break the image information down into meaningful components, and thereby perceive the nature of the objects in view."...

Diese Erkenntnis hat mir den Unterschied zwischen dem starken Kontrastanstieg "im Auge des Betrachters" und dem was einem die Physik im Kopf sagt : Es kann nicht soviel sein,höchstens die Unterdrückung der Raumeinflüsse.
Doch das visuelle System des Menschen besteht aus Auge+Gehirn als Datenverarbeitung.
Wenn jetzt bestimmte Rahmenbedingungen vom Üblichen abweichen,erfindet das Gehirn manchmal visuelle Eindrücke dazu zur Kompensation.
Dies ist die Grundlage aller visuellen Täuschungen und auch der Grund für das gewisse Extra an Kontrast im Auge des Betrachters.