Optical illusion
 

Spehen's Flower shot comments reminded me of this link.

An Interesting effect.

http://bobatkins.com/photography/tec..._illusion.html

Very interesting - you cannot believe your eyes!!

That was fascinating, thanks for the link robski.

Wonderful link. Thanks Rob.

BTW I am not at all surprise. I learned very well about the eyes illusion and the kind of moron I am long back dating back to the time I married my beloved wife. Good she is not reading this or if she does, Honey my account is been hacked...

hate to be a spoilsport, but only the dark squares in no shadow and light ones in FULL SHADOW are 120/120/120. The light ones are otherwise 206/206/206. The dark ones in shadow are 62/62/62. Also a thicker 120/120/120 bar only matches the dark squares as expected. The illusion ONLY applies to squares A & B and other light squares in full shadow, ie it amounts to a visual underestimation of the degree of shade. A selection 120/120/120 copied to the edge of shade sticks out.

Thats what my wife says so it must be right! :)

I am still not out of illusion caused by using real vs user name so may be that is why I don't either understand it. Chris can you please in plain simple English tell me what is your point? Optical illusion in your opinion is rightly an illusion or rightly it is a wrong illusion or its a delusion not illusion, il-defined illusion... Sorry I am confused..:confused:

This is about visual perception of luminance, which to the eye is comparative, ie takes account of the lighter or darker background around a specific patch of the picture. The computer on the other hand measures the absolute values, which I have recorded above.

You can get do an equivalent simple exercise on human perceptions of heat compared to thermometer readings by filling 2 bowls of water with cool and fairly hot water. Dipping your hands in in different sequences gives you a very different impression of the temperatures of the 2 bowls than if you stuck a thermometer in.

BTW no spelling mistakes as I am taking notice of FF2 underlines. Try the counter-intuitive approach that solved my FF problem ie if you want the spell-checker ON, TURN IT OFF, quit and restart. Now turn it on & next time it may work.