awpaeth@watcgl.waterloo.edu (Alan W. Paeth) (05/15/88)
(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
jtk@mordor.s1.gov (Jordan Kare) (05/17/88)
In article <4433@watcgl.waterloo.edu> awpaeth@watcgl.waterloo.edu (Alan W. Paeth) writes: >(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). > >Incidentally, ... the >aberration chart ... 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. In El Cerrito, CA, there is a building on Fairmont Ave. which has a large (several foot high) sign composed of internally lit letters. The letters are deep blue, and the sign as a whole is visible for several blocks. However, it is also completely illegible, and (at least to my eyes, which are beginning to have some distance vision problems as I age, although I've never worn glasses) appears as a large blue blur until you get very close, whereupon it finally resolves into the words EYE CENTER :-) Jordin (The Eternal Optometrist) Kare jtk@mordor.UUCP jtk@mordor.s1.gov