Quote:
Originally Posted by Krystian Galaj
However, I should think that with such additional bright light, the amount of light entering my eyes would be even greater - so why am I not getting headaches then?
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I'm not sure if you actually read my explanation, or you just missed the part about the eyes adjusting to the amount of light. That is done by modifying the size of your pupil.
Let's say that the amount of light coming from a light emitting screen (that you are looking at in the dark) is focused on 10% or your retina. Let's call the amount of light that falls in this case on 1% of your retina, right in the middle where the image is focused "P" for pain.
Now you turn on the light making the room as bright as the screen. That means that if the pupil would be the same size, you would have the same "P" amount of light, now for every % of your retina. However, the iris contracts, making the pupil smaller, so that the same amount falls in sum on the whole of your retina, that means that in this example your pupil will be reduced to 1/10. That means that for the 1% of the area in the center of where the image is focused you now get 10%P from the screen + 10% from the ambient light=20%P.
Obviously, you can look 5 times longer at the screen in a brightly lit room.
