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From: awpaeth@watcgl.waterloo.edu (Alan W. Paeth)
Newsgroups: sci.electronics,sci.astro
Subject: Re: Seeing UV
Message-ID: <4433@watcgl.waterloo.edu>
Date: 15 May 88 01:33:10 GMT
References: <230@snjsn1.SJ.ATE.SLB.COM> <702@eos.UUCP>
Reply-To: awpaeth@watcgl.waterloo.edu (Alan W. Paeth)
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Organization: U. of Waterloo, Ontario
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(re: discussions on the world as seen by people lacking the eye's crystalline
lens and on the ability to focus on the blue end of the spectrum).

I've often wondered what cataract viewers see, and what we normal folk are
missing -- off in the near UV where bees see pollen and such. Then I came
across this month's issue of "Sky and Telescope". The author of their deep
sky splendors column has had such surgery and boasted (I felt) that it added
some violets to certain nebula (The Crab?). He removes his glasses and any
eyepices and gets "prime focus" projection directly onto his retina!
Presumably he is using a reflecting telescope so that the image plane for UV
coincides with the visible.

The previous poster referenced Wysezeki and Stiles on UV vision and lens
flourescence. Two months ago I had to opportunity to visit the CNRC (Canadian
National Research Council) optics lab and colorimetry section, and saw
(through) the special glasses Wysezeki designed which provide achromatic
correction for a standard observer. These are "no power" chromatic correcting
lenses (afocal triplets, I also viewed through a seven element afocal
"eyepiece"). As near as I could tell with my 20/15 corrected vision, the
lenses did absolutely nothing.

This was Wysezeki's previous conclusion (while still alive); he had considered
marketing them. But note, I've seen JS&A (those gizmo-widget folks) advertise
special "minus blue" specs which are supposed to significantly improve contrast.
* They won't get any of my money! *

Incidentally, the lens prescription appears in that volume, together with the
aberration chart which puts people a good two or three diopters out in the far
blue. I've occasionally seen the effect -- it is maxmized when looking at blue
lettering on a dark surround viewed at infinity (closer than about 6 ft. and
your eye can accomodate). The most memorable example was blue computer graphics
lettering done in a 35mm slide presentation, but in all fairness, the slide was
designed to illustrate the effect.

    /Alan Paeth
    Computer Graphics Laboratory
    University of Waterloo