optical phenom

I had cataract surgery in one eye and will do the other one soon.

I have a pretty high power 400 nm laser. If I shoot it at the wall,
the dot is bright with the repaired plastic-lens eye and invisible
with the one that has the cataract. My doctor explained that a
cataract absorbs blue light, and that's why some old ladies color
their hair bluish-white, because then it looks right to them.

If I scan the laser around the room, some objects do show with the bad
eye and some don't. That's because many "white" objects fluoresce to
make them look whiter. Most things fluoresce greenish or purplish, but
the giant old Radiotron Designers Handbook fluoresces red.

I have a 4FP7 CRT (DuMont, square-face, long-persistance, PDA) on a
bookshelf and I can paint fun patterns on it.

That nearly-UV laser always gives me a mild headache.



-- 

I yam what I yam - Popeye

jlarkin@highlandsniptechnology.com wrote: 

> I had cataract surgery in one eye and will do the other one soon. 

You will clearly see the difference. 

Modern medicine is amazing, that is a good example. Assuming everything 
goes well. 

I woke up during mine. Could see some pixelated lights or whatever.
Couldn't feel a thing. The doctor said "don't talk". I should have said
"I'll be back" but instead I just shut up and went back to sleep. 

On Wednesday, April 13, 2022 at 10:09:58 AM UTC+10, jla...@highlandsniptechnology.com wrote:
> I had cataract surgery in one eye and will do the other one soon. 

My wife had both her lenses replaced, and commented on the improvement in her colour vision. The colours got a lot more subtle, what ever that means.

My optician assures me that I do have cataracts,  but they aren't bad enough to be noticeable, let alone to be worth doing anything about.

-- 
Bill Sloman, Sydney

BTW... At the same time, they can remove "floaters" too.

On a sunny day (Tue, 12 Apr 2022 17:09:47 -0700) it happened
jlarkin@highlandsniptechnology.com wrote in
<034c5hh182v4dj8cqurtaj6fgqs21uu14i@4ax.com>:

>I had cataract surgery in one eye and will do the other one soon.
>
>I have a pretty high power 400 nm laser. If I shoot it at the wall,
>the dot is bright with the repaired plastic-lens eye and invisible
>with the one that has the cataract. My doctor explained that a
>cataract absorbs blue light, and that's why some old ladies color
>their hair bluish-white, because then it looks right to them.
>
>If I scan the laser around the room, some objects do show with the bad
>eye and some don't. That's because many "white" objects fluoresce to
>make them look whiter. Most things fluoresce greenish or purplish, but
>the giant old Radiotron Designers Handbook fluoresces red.
>
>I have a 4FP7 CRT (DuMont, square-face, long-persistance, PDA) on a
>bookshelf and I can paint fun patterns on it.
>
>That nearly-UV laser always gives me a mild headache.

I have one of those LED UV flashlight to check banknotes
It looks bluish to me.
 When it shines on normal white paper it lights up brighter bluish -white.
  https://www.ebay.com/itm/112135829056

PS
it is actually fun stuff, UV,
 https://www.thoughtco.com/what-glows-under-a-black-light-607615

I tried it among other things on London Tonic.. the quinine in it lights up.
Also my old EPROM eraser lightbulb works the same way, but is better more powerful UV I think,
do not look into it.

Am 13.04.22 um 02:09 schrieb jlarkin@highlandsniptechnology.com:
> I had cataract surgery in one eye and will do the other one soon.
> 
> I have a pretty high power 400 nm laser. If I shoot it at the wall,
> the dot is bright with the repaired plastic-lens eye and invisible
> with the one that has the cataract. My doctor explained that a
> cataract absorbs blue light, and that's why some old ladies color
> their hair bluish-white, because then it looks right to them.
> 
> If I scan the laser around the room, some objects do show with the bad
> eye and some don't. That's because many "white" objects fluoresce to
> make them look whiter. Most things fluoresce greenish or purplish, but
> the giant old Radiotron Designers Handbook fluoresces red.
> 
> I have a 4FP7 CRT (DuMont, square-face, long-persistance, PDA) on a
> bookshelf and I can paint fun patterns on it.
> 
> That nearly-UV laser always gives me a mild headache.


Reminds me at a guy in France some 200 years ago who discovered
color blindness from the fact that he and his brother classified
the color of flowers differently than other people, depending
on sunlight or candles.

Gerhard

On Wednesday, 13 April 2022 at 07:19:56 UTC+1, Gerhard Hoffmann wrote:
> Am 13.04.22 um 02:09 schrieb jla...@highlandsniptechnology.com:
> > I had cataract surgery in one eye and will do the other one soon. 
> > 
> > I have a pretty high power 400 nm laser. If I shoot it at the wall, 
> > the dot is bright with the repaired plastic-lens eye and invisible 
> > with the one that has the cataract. My doctor explained that a 
> > cataract absorbs blue light, and that's why some old ladies color 
> > their hair bluish-white, because then it looks right to them. 
> > 
> > If I scan the laser around the room, some objects do show with the bad 
> > eye and some don't. That's because many "white" objects fluoresce to 
> > make them look whiter. Most things fluoresce greenish or purplish, but 
> > the giant old Radiotron Designers Handbook fluoresces red. 
> > 
> > I have a 4FP7 CRT (DuMont, square-face, long-persistance, PDA) on a 
> > bookshelf and I can paint fun patterns on it. 
> > 
> > That nearly-UV laser always gives me a mild headache.
> Reminds me at a guy in France some 200 years ago who discovered 
> color blindness from the fact that he and his brother classified 
> the color of flowers differently than other people, depending 
> on sunlight or candles. 
> 
> Gerhard
We had a workman in the house once who mentioned that he was
colour blind and could not see red at all.  The sun was shining on
a cut glass ornament projecting a spectrum on the wall.  He pointed
out the regions of the spectrum that he could see.  The red end really
was completely missing.

John

In article <t35q24$qlfe$1@solani.org>, dk4xp@arcor.de says...
> 
> Reminds me at a guy in France some 200 years ago who discovered
> color blindness from the fact that he and his brother classified
> the color of flowers differently than other people, depending
> on sunlight or candles.
> 
> Gerhard

What a co-incidence. Because as Wikipedia relates 
(<https://en.wikipedia.org/wiki/Color_blindness>), John Dalton and his 
brother in Manchester, England, also noticed the same thing. And colour-
blindness is known as Daltonism after him... Dalton is known for lots of 
other topics and admittedly, Wikipedia says: "In 1822 he paid a short 
visit to Paris."

On 13/04/2022 01:09, jlarkin@highlandsniptechnology.com wrote:
> I had cataract surgery in one eye and will do the other one soon.
> 
> I have a pretty high power 400 nm laser. If I shoot it at the wall,
> the dot is bright with the repaired plastic-lens eye and invisible
> with the one that has the cataract. My doctor explained that a
> cataract absorbs blue light, and that's why some old ladies color
> their hair bluish-white, because then it looks right to them.
> 
> If I scan the laser around the room, some objects do show with the bad
> eye and some don't. That's because many "white" objects fluoresce to
> make them look whiter. Most things fluoresce greenish or purplish, but
> the giant old Radiotron Designers Handbook fluoresces red.

Red is fairly unusual fluorescence with 400nm excitation.

The colours you get tend to vary with rare earth impurities or various 
aromatic dyes. Washing powders contain a fairly potent blue fluorescer.

Bank notes and secure paper contain interesting flecks that show under 
the right wavelength of near UV light.

> I have a 4FP7 CRT (DuMont, square-face, long-persistance, PDA) on a
> bookshelf and I can paint fun patterns on it.
> 
> That nearly-UV laser always gives me a mild headache.

400nm is a wavelength capable of harming human eyes at high levels.

The solar Calcium K line filter at 394nm is sold as suitable only for 
photographic use for that reason. Eye damage is a real risk.

https://www.baader-planetarium.com/en/baader-k-line-filter-1¼"-(double-stacked).html

Spec sheet has more info on the potential hazards at this wavelength:

https://www.baader-planetarium.com/en/downloads/dl/file/id/8/product/1399/important_notes_on_the_stacked_k_line_filter.pdf


-- 
Regards,
Martin Brown