Re: [Phys-l] FW: Science show "Humanly Impossible" on NationalGeographic channel.

[Bernard Cleyet <bernardcleyet@redshift.com>]

> Is "sharpness" here equated with angular resolution?  If so,  
> wouldn't a
> larger pupil/aperture result in better resolution?

Yes and no (as Rick below).  The representative modulation transfer  
function of the  eye is plotted in Levi (1).   At the smallest  
diameter (2.0 mm) the limit is diffraction above about 25 c/deg (2)   
(about the same as the 2 mm Airy disk (3)) below that it is the  
superior.  Above ~ 25 c/deg 3.0 mm is the superior.   3.8 mm is  
better than all (max. given is 6.6 mm) but 3.0 mm above 30 c/deg.

Summary:  Not the brightest illumination for fine work.     The MIL- 
HDBK-141 p. 4-6 gives max. resolving power at ~ 30  foot-lamberts  
decreasing thereafter with increased illumination.

Spherical aberration is considerably less than expected for the Le  
Grand model (4) which assumes spherical surfaces.  Why?  Because,  
contrary to Rick below, God is an optician.  The std. eye's cornea is  
flattened away from its apex and its refractive index lessens toward  
its edge.  (3)

More for those w/o Levi or similar reference:  unaccommodated eye SA  
is:   delta V = ~ 0.16 (R mm)^2 diopter.   r measured from the apex.   
During accommodation SA lessens and may even change sign.  Chrom. ab.  
is another matter.  ~ 2.5 D   between 0.4 => 0.7 micron.    No  
matter, as mentioned, the brain is half? of seeing.   Levi devotes  
almost 100 pp to vision.





(1) Applied Optics V. 2,  p.375 and reference:  Campbell and Gubish,  
Optical quality of the human eye  J. Physiol. (Lond.) v. 186 pp.  
583-578 (1966)
(2) cycles (line pair)/deg.
(3) op. cit. p 374
(4)  http://www.optics.arizona.edu/Opti510L/references/eye%20models.pdf

 http://www.opticsinfobase.org/abstract.cfm?URI=josaa-2-8-1273



bc, contrary to the above, is still an extremely and aggressively   
devout atheist.



On 2009, Nov 18, , at 07:19, Rick Tarara wrote:

> The eye's lens (and cornea) introduce a good deal of spherical
> aberration--guess mother nature doesn't have all of the lens grinder's
> equations down pat!  One way to increase the acuteness of focus is  
> to use
> only the center of the lenses--you want the opposite of dilation.   
> The iris
> will close down with lots of light--hence for fine work you want  
> that work
> to be very well illuminated.
>
> Rick
>
> ***************************
> Richard W. Tarara
> Professor of Physics
> Saint Mary's College
> Notre Dame, IN
> rtarara@saintmarys.edu
> ******************************
> Free Physics Software
> PC & Mac
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> *******************************
> ----- Original Message -----
> From: "Michael Meyer" <mrmeyer@mtu.edu>
> To: "Forum for Physics Educators" <phys-l@carnot.physics.buffalo.edu>
> Sent: Wednesday, November 18, 2009 9:14 AM
> Subject: Re: [Phys-l] FW: Science show "Humanly Impossible" on
> NationalGeographic channel.
>
>
> > John Clement wrote:
> >
> > "Dilate means to make larger, so pupils do the opposite to sharpen  
> > vision.
> > Remember the optometrist dilates the pupils to be able to look  
> > inside the
> > eye.  But pupils dilate when you see something of interest which  
> > increases
> > the amount of light at the same time the sharpness is decreased."
> >
> > Is "sharpness" here equated with angular resolution?  If so,  
> > wouldn't a
> > larger pupil/aperture result in better resolution?
> >
> > Mike Meyer
> > Lecturer/Lab Coordinator
> > Michigan Tech University
> > mrmeyer@mtu.edu
> > _______________________________________________
> > Forum for Physics Educators
> > Phys-l@carnot.physics.buffalo.edu
> > https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l
>
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