Re: Urban Fables: Stellar by Sunlight

["QUIST, OREN" <OREN_QUIST@SDSTATE.EDU>]

You say "better resolution" which is a good way to put it, but the way I
explain it is to say that the pinhole effect increases the "depth of field"
so that everything is in focus.

-----Original Message-----
From: Larry Cartwright [mailto:exit60@CABLESPEED.COM]
Sent: Wednesday, March 27, 2002 10:10 AM
To: PHYS-L@lists.nau.edu
Subject: Re: Urban Fables: Stellar by Sunlight


Gary Turner wrote:
> Incidentally, I have been told that squinting helps seeing because
> it restricts the entering light - causing the pupils to dilate and
> improving the available resolution.  Is there any truth to this?

I don't believe it has anything to do with dilating the pupils.  When
you squint, your eyelids and lashes cover most of the pupil; so it
doesn't matter whether the pupil is dilated or not.

I've always thought that squinting lets the lids and lashes form
essentially "pinholes", which produces an image on the retina much as a
pinhole camera produces an image on a piece of film no matter how long
or short the camera box.  The smaller the pinhole, the better the
resolution of the image.  I'm ready and waiting to be educated by
someone who can point out where I have gone wrong.

Best wishes,

Larry

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Larry Cartwright   <exit60@cablespeed.com>
Retired (June 2001) Physics Teacher
Charlotte MI 48813 USA
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