How big is our normal blind spot?

How big is it if you look at things from, let's say, a 5 yard distance?

 

Close your eyes and it's huge.

 

You really should be talking about subtended angles. The blind spot is 5
degrees wide and 7 degrees high according to Bennett and Rabbetts. An old
astronomer's trick for measuring angles is the width of a closed fist at
arm's length is 10 degrees. So my question is, how are you measuring the
blind spot?

Don W.

 

Exactly how did you do that?

Don W.

 

If I take the conventional 3" x 5" card and put a "dot" and a "+" on it
(couple of inches apart) to check the blind spot, I get the "+" to disappear
at about 8 inches looking at the "dot" . Now if I just run a vertical line
thru the "+" to cover the entire card, I can get the "+" to disappear, but
the line stays intact continuous, but no horizontal part of the "+").
Interesting computational fill in. So if you are looking at a 10" book at 5
feet, that covers 9 degrees, which exceeds the blind spot dimension. So I
would say it was lucky your book disappeared.

Don W.