Naked Science Forum

Life Sciences => Physiology & Medicine => Topic started by: Mazurka on 16/11/2011 13:19:29

Title: Seen out of the corner of my eye?
Post by: Mazurka on 16/11/2011 13:19:29

I spent this morning watching a (dull) presentation. 

I was sat at an angle to the projector and screen and had an oblique view of the projector.  I could not help but notice that when I glanced at the projector lens,  I would see the red green blue, but if I looked at it I would see white.

No matter how hard I tried, I could only get a momentary glimpse of the red green blue and could not focus on it.

Why is this?



   

Title: Seen out of the corner of my eye?
Post by: Bored chemist on 16/11/2011 21:32:45

The projector gives a red image, then a green one then a blue on in rapid succession. With a quick glance you only see one colour or a blurred multi colour image.

Title: Seen out of the corner of my eye?
Post by: Geezer on 17/11/2011 06:04:05

It's because your peripheral vision is much better at detecting changes, which is probably an evolutionary advantage. If you look at an old fangled TV with your peripheral vision, you might be able to see it flicker.

Those of us old enough to remember what oscilloscopes were would sometimes take advantage of that technique to observe very faint pulses as they were painted on the CRT screen.

Title: Seen out of the corner of my eye?
Post by: Mazurka on 17/11/2011 10:02:23

Thanks.

With a quick glance it was like seeing the light spectrum through a prism but without the orange, yellow, indigo, violet parts and it seemed remarkably sharp (although that could have been an effect of brightness)

I am inclined to agree that it is an effect of peripherhal vision, but I thought that the cones (colour sensitive cells) were concentrated around the fovea "sweet spot" of focuse vision and the rods (monochrome) were more sensitive to movement / low light.