Sorry about the delay.

I am not sure. If you think about it, overlapping colours don't go along
with the topology of stress lines.
However, cellophane tape is a different situation. It could be that
the perception of the colour magenta is situational like
the perception of yellow.

Did you know that a third class of mammalian photoreceptors was discovered
in the 1990's?
Intrinsically photosensitive retinal ganglion cell were only shown to be
definitively present in humans in 2007 in people who were born without rods
and cones.

>From wikipedia " ipRGCs were only definitively detected in humans during
landmark experiments in 2007 on rodless, coneless humans.[15]
<> As had
been found in other mammals, the identity of the non-rod non-cone
photoreceptor in humans was found to be a ganglion cell in the inner
retina. The researchers had tracked down patients with rare diseases wiping
out classic rod and cone photoreceptor function but preserving ganglion
cell function.[15]
<> Despite
having no rods or cones the patients continued to exhibit circadian
photoentrainment, circadian behavioural patterns, melanopsin suppression,
and pupil reactions, with peak spectral sensitivities to environmental and
experimental light matching that for the melanopsin photopigment. Their
brains could also associate vision with light of this frequency."


On Wed., Aug. 16, 2023, 5:31 p.m. MSF, <> wrote:

> Would it change your mind if you saw the real thing instead of a digital
> representation? All of color photography, both on film and now with digital
> cameras and LCD or OLED screens depend upon acceptable approximations of
> the real colors.  This varies among different cultures.
> And now, I delve once more into my misty past. In the late 60s I made a
> meager living doing what was then called a "psychedelic light show" with
> rock bands.  One of the effects I used was a rotating polarizer combined
> with various crystals and injection molded styrene. I used to search
> grocery and hardware stores for suitable pieces. I would then use them as
> is or further stress them by heating and stretching. You can definitely see
> edges of red and blue around the magenta. Something even more definitive
> could be seen when making patterns from the original Scotch cellophane
> tape. After they switched to polypropylene, much to my disappointment at
> the time, the effect was no longer possible. As you rotate the polarizer
> slowly you could see a washed out red, fading into magenta and then blue.
> Again, probably more than you wanted to know.
> ------- Original Message -------
> On Wednesday, August 16th, 2023 at 2:16 AM, H L V <>
> wrote:
> Cool. Your story got me to watch videos of stress visualization in plastic
> using polarized light.
> Noticing how readily the colour magenta (a.k.a. pink ) is produced in this
> video as the plastic is rotated.
> Watching how the magenta patches come and go as the viewing angle changes
> got me thinking about the common teaching that since magenta does not
> appear in Newton's spectrum it is made up by the brain whenever red and
> blue light overlap. (By contrast magenta does appear in Goethe's spectrum
> a.k.a the dark spectrum).
> Although it is certainly possible to trick the brain into seeing colours
> which aren't there such as when red and green light overlap to create the
> illusion of yellow light, this is not proof that magenta is just made up by
> the brain. On the contrary if magenta were just made up by the brain then
> _every_ instance of magenta in the above video should show signs of red and
> blue around its perimeter which is not the case.
> Harry
> On Mon, Aug 14, 2023 at 5:16 PM MSF <> wrote:
>> More polarized fun...
>> A much more easily viewed demonstration of the effect we are discussing
>> here is looking at clear glass table tops outside. If you happen to have
>> some lawn furniture that includes a clear tempered glass table top, all you
>> have to do is stand to the east or west of of the glass and look down at it
>> at an angle of approximately 56 degrees and you will see beautiful pools of
>> color. The colors outline the birefringence caused by the strains in the
>> tempered glass.
>> Once in a while a random observation at my back yard of the phenomenon by
>> a friend or family member will be alarmed at "something wrong with the
>> glass". And of course, their eyes glaze over when I try to explain it.
>> You might wonder why I immediately recognized Harry's noticing of
>> mysterious color effects during his walk. It's simple. When I was very
>> young, I used to see these colors in the pavement all the time, directly
>> on, not peripherily. The reason is my brother and I were blessed, or
>> cursed, with vision that was so sharp and light sensitive that we were
>> accused all the time of "seeing things". We tested out at 20-05 on the eye
>> charts. Our retinas must have been so stuffed withe rods and cones, I'm
>> surprised they didn't explode. I could see close to 7th magnitude stars.
>> That's all gone now that I'm old. Down to 20-20 with lens implants.
>> Please pardon my self-indulgent nostalgia.
>> MSF

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