It seems to me that you are still using the word colour in a way that suggests you haven’t really grasped the insight that makes this illusion seem not-bizarre. That insight is fundamentally that the statement “this ball is blue” is not equivalent to the statement “a digital photo of a scene containing this ball would have pixel values of 0, 0, 255 at pixel locations where light from the ball reached the sensor”. It is a much more complex (and more useful) statement than that. The bad assumption is that ‘colour’ when used to refer to a property of objects in the world determined through visual perception has any simple relationship with RGB values recorded by a digital camera. You still seem to be talking as if RGB values are somehow ‘true’ colours.
The bad assumption is that ‘colour’ when used to refer to a property of objects in the world determined through visual perception has any simple relationship with RGB values recorded by a digital camera.
I think the key for me in understanding this type of illusion (and the general phenomenon of colour constancy) was to realize that ‘colour’ in common usage (“this ball is blue”) is perceived as a property of objects and we infer it indirectly based on light that reaches our retinas. That light also has a ‘colour’ (subtly different meaning) but it is not something we perceive directly because it is not very useful in itself.
This makes perfect sense when you think about it from an evolutionary perspective—we evolved to recognize invariant properties of objects in the world (possibly fruit in trees for primates) under widely varying lighting conditions. Directly perceiving the ‘colour’ (RGB) of light would not tell us anything very useful about invariant object properties. There is enough overlap between the two meanings of colour for them to be easily confused however and that is really the root of this particular illusion.
In computer graphics we commonly use the term ‘material’ to describe the set of properties of a surface that govern how it responds to incident light. This encompasses properties beyond simple colour (“shiny blue ball”, “matte blue ball”, “metallic blue ball”). I don’t know if that usage is well understood outside of the computer graphics field however.
I completely agree with you. At this point, I am just trying to clean up the article to help clarify the answer behind the illusion. Does the phrase, “I should stop thinking that the visual system is reporting RGB style colors” mesh okay? That is the only location of RGB as of this edit.
Thanks. Do you have any other suggestions that may help clarify the article? Your explanations have been very helpful. Learning the terms was apparently something I never bothered to do. Oops. :P
I think the key for me in understanding this type of illusion (and the general phenomenon of colour constancy) was to realize that ‘colour’ in common usage (“this ball is blue”) is perceived as a property of objects and we infer it indirectly based on light that reaches our retinas.
This happened sometime this morning. The more I read here, the more I understand it in the sense that I know the name of the relevant field, a whole bunch of new terms, and more details about how we perceive colors. It gets less and less bizarre as the day goes, which is always fun. :)
It seems to me that you are still using the word colour in a way that suggests you haven’t really grasped the insight that makes this illusion seem not-bizarre. That insight is fundamentally that the statement “this ball is blue” is not equivalent to the statement “a digital photo of a scene containing this ball would have pixel values of 0, 0, 255 at pixel locations where light from the ball reached the sensor”. It is a much more complex (and more useful) statement than that. The bad assumption is that ‘colour’ when used to refer to a property of objects in the world determined through visual perception has any simple relationship with RGB values recorded by a digital camera. You still seem to be talking as if RGB values are somehow ‘true’ colours.
Especially in the case of human tetrachromats.
I am trying to find a way to say what you said with one phrase or word. I feel like I am struggling to find a term.
I think the key for me in understanding this type of illusion (and the general phenomenon of colour constancy) was to realize that ‘colour’ in common usage (“this ball is blue”) is perceived as a property of objects and we infer it indirectly based on light that reaches our retinas. That light also has a ‘colour’ (subtly different meaning) but it is not something we perceive directly because it is not very useful in itself.
This makes perfect sense when you think about it from an evolutionary perspective—we evolved to recognize invariant properties of objects in the world (possibly fruit in trees for primates) under widely varying lighting conditions. Directly perceiving the ‘colour’ (RGB) of light would not tell us anything very useful about invariant object properties. There is enough overlap between the two meanings of colour for them to be easily confused however and that is really the root of this particular illusion.
In computer graphics we commonly use the term ‘material’ to describe the set of properties of a surface that govern how it responds to incident light. This encompasses properties beyond simple colour (“shiny blue ball”, “matte blue ball”, “metallic blue ball”). I don’t know if that usage is well understood outside of the computer graphics field however.
I completely agree with you. At this point, I am just trying to clean up the article to help clarify the answer behind the illusion. Does the phrase, “I should stop thinking that the visual system is reporting RGB style colors” mesh okay? That is the only location of RGB as of this edit.
Yes, I think ‘RGB colours’ is better than ‘True Colours’ in this context.
Thanks. Do you have any other suggestions that may help clarify the article? Your explanations have been very helpful. Learning the terms was apparently something I never bothered to do. Oops. :P
The article reads better now. So do you feel the bizarreness has disappeared now you understand the phenomenon better?
Yes. The key point that you mentioned here:
This happened sometime this morning. The more I read here, the more I understand it in the sense that I know the name of the relevant field, a whole bunch of new terms, and more details about how we perceive colors. It gets less and less bizarre as the day goes, which is always fun. :)
How is “Color gross of lighting conditions”?