Naked Science Forum

Life Sciences => Physiology & Medicine => Topic started by: BAGappa on 01/04/2009 23:48:52

Title: Glowing Letters
Post by: BAGappa on 01/04/2009 23:48:52

I was reading a book out in the sun today and the white page was really bright, so I had to squint. After a few minutes the sun snuck behind a cloud and the black text on the page seemed to have a yellow glow around it. Why does this happen?

Title: Glowing Letters
Post by: neilep on 02/04/2009 00:16:14

I don't know the science but this is not an effect on the page you were reading this is a ' eye biology' thing happening !

You see it in a lot of illusions...

...I am sure someone who knows about it will explain it all very soon !!

Title: Glowing Letters
Post by: Karen W. on 04/04/2009 14:54:46

You should also use sunglasses as the pages will reflect the sun back into your eyes.. I would think it could actually hurt your eyes... I am no expert but you know how snow can burn your face with the light reflecting off the snow back to your face.. It, I would think is the same principle. So I would wear my Sun glasses to shade my eyes from the reflection from the page... [;)] [:)]

Title: Glowing Letters
Post by: Variola on 05/04/2009 13:31:23

Glowing letters???

Title: Glowing Letters
Post by: RD on 05/04/2009 13:49:57

The light aura around black letters is part of the negative afterimage (http://en.wikipedia.org/wiki/Afterimage).
The eye constantly makes tiny movements (microsaccade (http://en.wikipedia.org/wiki/Microsaccade)) this is why parts of the negative (after)image appear as an aura. If the eye did not make these tiny movements the negative image would be in perfect register with the original and there would be no aura, just lower contrast.