Editing Color constancy (section)

== Object illuminance ==
The phenomenon of color constancy occurs when the source of illumination is not directly known.<ref name=":1">{{cite journal | last1 = Foster | first1 = David H. | year = 2011| title = Color Constancy | journal = Vision Research | volume = 51 | issue = 7| pages = 674–700 | doi = 10.1016/j.visres.2010.09.006 | pmid = 20849875 | s2cid = 1399339 | doi-access = free }}</ref> It is for this reason that color constancy takes a greater effect on days with sun and clear sky as opposed to days that are overcast.<ref name=":1"/> Even when the sun is visible, color constancy may affect [[Color vision|color perception.]] This is due to an ignorance of all possible sources of illumination.  Although an object may reflect multiple sources of light into the eye, color constancy causes objective identities to remain constant.<ref name="Jameson 1989">{{cite journal | last1 = Jameson | first1 = D. | last2 = Hurvich | first2 = L. M. | year = 1989 | title = Essay concerning color constancy | journal = [[Annual Review of Psychology]] | volume = 40 | pages = 1–22 | doi=10.1146/annurev.psych.40.1.1| pmid = 2648972 }}</ref>

D. H. Foster (2011) states, "in the natural environment, the source itself may not be well defined in that the illumination at a particular point in a scene is usually a complex mixture of direct and indirect [light] distributed over a range of incident angles, in turn modified by local occlusion and mutual reflection, all of which may vary with time and position."<ref name=":1"/> The wide spectrum of possible illuminances in the natural environment and the limited ability of the human eye to perceive color means that color constancy plays a functional role in daily perception.  Color constancy allows for humans to interact with the world in a consistent or veridical manner<ref>{{cite book |last=Zeki |first=Semir |year=1993 |title=A vision of the brain |location=Oxford |publisher=Blackwell Science Ltd.|isbn=0632030542}}{{page?|date=August 2024}}</ref> and it allows for one to more effectively make judgements on the time of day.<ref name="Jameson 1989" /><ref>{{cite journal | last1 = Reeves | first1 = A | year = 1992 | title = Areas of ignorance and confusion in color science | journal = Behavioral and Brain Sciences | volume = 15 | pages = 49–50 | doi=10.1017/s0140525x00067510| s2cid = 146841846 }}</ref>