P3D Re: 2519 - focus (Dr. T)

["Greg Wageman" <gjw@xxxxxxxxxx>]

From: Dr. George A. Themelis <DrT-3d@xxxxxxxxxxxxxxxxxxxxxxxxxxx>


>>Are we certain about this?  ...  my observations indicate to me the
>>following: When we "focus on" (perhaps "pay attention to" would be a better
>>way to put it) a foreground element in a scene in "real life," the background
>>is not "out of focus" (i.e., "blurred"), but rather our visual perception of
>>it is doubled.
>
>I was repeating an indirect statement made by someone else but, yes, I am
>certain about this.  When we "pay attention to" something, the eyes
>perform two functions:  First they converge at this something, second
>they accommodate (focus on it).


But, George, you're ignoring the depth of focus of the human eye.  In full sun,
the pupil diameter is very small (I don't know what the equavalent f-number is,
but I'd guess it's large).

>>When I close one eye and concentrate on either the finger or the
>>background, neither is blurred nor doubled.


Jim's observations agree with mine... in fact he posted almost exactly the same
"experiment" as I did.

     -Greg W. (gjw@xxxxxxxxxx)



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