Opponent process theory: why do I see green after looking at white?

[DeuteriumDude]

This morning, I was lying on my bed, looking at the bright morning light coming in through the window. The blinds (which are white) were at least half shut, so much of the light was filtered through them. I then stared up at the ceiling, and saw a nebulous patch of green. I shut my eyes, and the nebulous patch of green became clearer still. I then reopened my eyes, looking again at the ceiling, and the nebulous patch became purple.

Here's what I don't understand: shouldn't the nebulous patch be black, since I was originally looking at something white? A green patch should be left by staring at purple. There is nothing purple in my room or outside my window. And yet, I've had this happen to me before while reading a book under bright sunlight: eventually, everything in my field of vision will look green. Also, why does the nebulous patch turn purple when I shut and reopen my eyes? None of these things seem to follow the predictions of opponent process theory.

 

[Hedwig]

My first thought is that you are seeing green in response to red; the eyelids are very thin and full of blood vessels, so if you close the lids while strong light is shining on them, you may be aware that the darkness under the lids is red-tinted if you have the eyes positioned as if to see (not rolled back).

 

[Lievo]

Dude, take care of your eyes.

Here's what I don't understand: shouldn't the nebulous patch be black, since I was originally looking at something white? (...) Also, why does the nebulous patch turn purple when I shut and reopen my eyes? None of these things seem to follow the predictions of opponent process theory.

Well this theory is about color perception in steady condition, while here you're playing with adaptation to dangerously bright lights. I'd guess the green switching to purple comes from the relative speed of adaptation of the three photoreceptors types, especillay the blue ones versus the two others.

 

[sanko]

Dude its very normal its just impression of bright light which remains in eyes its happens to indivisuals whose eyes are more sensetive to light like high myopics,or people with vit A Deficiency,zinc deficiency

 

[LudusRex]

Opponent process theory is a well-established psychological theory that explains color perception and afterimages. According to this theory, our visual system has three types of color receptors: red-green, blue-yellow, and black-white. These receptors work in opposition to each other, meaning that when one is stimulated, the other is inhibited. This is why we see complementary colors, such as green after staring at red, or yellow after staring at blue.

In your case, the white light from the window was stimulating all three types of receptors, but the red-green receptors were being stimulated the most due to the greenish tint of the light coming through the white blinds. When you shifted your gaze to the white ceiling, the red-green receptors were still overstimulated, causing the green afterimage. This is also why the afterimage became clearer when you closed your eyes, as the white light was no longer stimulating the receptors.

As for the purple afterimage, this can be explained by the principle of color constancy. Our brain automatically adjusts for changes in lighting, so even though the light coming through the window was greenish, our brain perceives it as white. When you shifted your gaze to the white ceiling, your brain was still adjusting for the greenish light, causing the afterimage to appear as its complementary color, purple.

Therefore, your experience is actually in line with opponent process theory. The afterimages you saw were a result of the overstimulation of certain color receptors and the principles of color constancy and complementary colors. I hope this explanation helps to clarify your experience.