Editing Ibn al-Haytham (section)

=== Color constancy ===
{{Main|Color constancy}}
Alhazen explained [[color constancy]] by observing that the light reflected from an object is modified by the object's color. He explained that the quality of the light and the color of the object are mixed, and the visual system separates light and color. In Book II, Chapter 3 he writes:<blockquote>Again the light does not travel from the colored object to the eye unaccompanied by the color, nor does the form of the color pass from the colored object to the eye unaccompanied by the light. Neither the form of the light nor that of the color existing in the colored object can pass except as mingled together and the last sentient can only
perceive them as mingled together. Nevertheless, the sentient perceives that the visible object is luminous and that the light seen in the object is other than the color and that these are two properties.<ref>{{Cite book |last1=Boudrioua |first1=Azzedine |url=https://books.google.com/books?id=WD0PEAAAQBAJ&dq=Al-Haytham+described+color+constancy+by+observing+that+light+reflected+by+an+object+is+modified+by+the+color+of+the+object&pg=PA78 |title=Light-Based Science: Technology and Sustainable Development, The Legacy of Ibn al-Haytham |last2=Rashed |first2=Roshdi |last3=Lakshminarayanan |first3=Vasudevan |date=2017|publisher=CRC Press |isbn=978-1-4987-7940-1 |language=en}}</ref></blockquote>