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[Jeremy McCreary]

Not to get too far off-topic, but curious about the stem diameters on these tops? Do you feel like you're getting a good angular momentum transfer when you twirl them?

The problem would be that they spin too fast, not slow enough for the visual system...

So these tops might benefit from thicker stems.

[Iacopo]

I didn't know about Fechner colors, I tried with one of my tops but I don't see them.
Looking better, at about 400-600 RPM, I see the colors, mainly yellow-green, in intricated and moving textures.
I used a spotlight on the top and staring at it the colors to me start to appear after about ten seconds. 


I found the following comment in YouTube, from the video linked below:


timwins31 wrote:

"The colors are called pattern induced flicker colors and the reason some people see them and others dont - and why those who do see them report seeing different colors from others - is related to your ganglion and cone cells in your eyes.  Ganglion detect fine movement or change - cones perceive color.  When ganglion detect change they activate the cones.  There are 3 types of cones each detecting a different range of color, short wavelength color, midlength, and long wavelength colors.  Think of is as red, blue, green for argument sake.  Each of the 3 cell types is able to detect color at a different speed, short being quickest and long the slowest, after the cell detects a color, it relays the information to the brain, then has a momentary reset, and then is ready to detect again.  The reset time is different for each of the 3 as well.  When the ganglion trigger them looking at a Benham disk, they don't detect color at first, so they reset and try again, over and over again, until the disk reaches the necessary speed to harmonize their 3 signals.  The harmonized signals cause neurons in the brain to align in a certain manner and for lack of a better term harmonize as well (the actual reason we see color when certain neurons synchronize and harmonize isn't well understood, it has something to do with allowing communication in the brain between two parts that don't typically communicate, like your visual sensory centers to communicate with your audible sensory centers - LSD has the same effect, that's why sometimes people report seeing sound in color form).  The result is the hallucination of color.  The reason some people see it and some don't is because we all have a different number of neurons and a different alignment of our neural networks.  If you don't have enough neurons or they aren't aligned in the required format, or if you have any kind of neurological disorder, you might not see the colors.  And just because you don't one time doesn't mean you won't next time.  The number of neurons changes depending on numerous factors but mainly overall health and lifestyle and age.  They also are constantly changing the alignment of your network structure.  So if there is enough change you can see them once and not the next time or vice versa.
(I did research on cone cell oscillation and on variance in cone cell activation speeds in elderly people while in college)."


Even staring at the video below some pale colors can be seen.  At first I thought that the colors are in the video, but pausing the video the colors disappear, so this is a real color illusion caused by the spinning of the disk.

[ta0]

This site has some Benham discs that can be printed with background colors that I have not tried yet: http://www.bu.edu/lite/Project_LITE_Spinning_Tops/LITE_Spinning_Tops.html




and two with unusual color mixing:

[Jeremy McCreary]

I have this set of optical illusion tops from Naef...

Video of this elegant B&W top set at https://kunstbaron.de/en/spinning-top-illusion-op-tric.html, where it's still sold. If the price tag weren't 78 Euros, I'd buy one!

[ta0]

Video of this elegant B&W top set at https://kunstbaron.de/en/spinning-top-illusion-op-tric.html, where it's still sold.

Good find that website, although the video itself is terrible (over-exposed and only shows some strobe effects due to the camera).
I need to ask somebody else if they see colors on these tops. I just spun them over a white paper, and after careful observation I could see on one of them a pink band at low speed that later changes to a cyan color and on another one a light green band. No colors on the other three. In contrast, I see several rings in clear reds and greens on The Toycrafter version.

The site has other tops from Naef for sale, as well as tops from well known top artist Armin Kolb (member of this forum) and Christoff Guttermann another top artist (whose statements about tops remind me those of Philippe Dyon). It includes a spinning top table by Guttermann for the serious top spinner (560 euros including VAT but plus shipping)  :

[Iacopo]

This site has some Benham discs that can be printed

I printed the first one and the one with a red background, (thanks for the link !), and I tried them.

I tried the first one in diffuse daylight, and no colors appear to me, apart from a slight tendency to violet in the outer ring.
The other three rings appear grey.  Interestingly, the brightness of the four rings is different, being the first and the last ones darker, and the other two ones in between brighter.  I didn't expect this, because, being the proportion between black and white the same in all the four rings, it would seem to me that the brightness in the four rings should remain the same.

Directing a spotlight, (warm tone, but what it matters seems the intensity of the light and not very much the tone), to the disk, colors appear:
In the first, inner ring, I see orange, brown, sometimes yellow. This is the ring with the strongest color.
In the second one, I see grey-green-blue.
In the third, I see grey-violet.
In the fourth, outer ring I see violet.
Again, the first and the last rings appear darker than the other two ones.
The colors seem more intense at approximately 500 RPM.  At other speeds the colors seem to be always the same, but more confused.

I tried to spin the top counterclockwise instead of clockwise:
I see exactly the same four colors but in reversed order, with orange in the outer ring and violet in the inner ring.

So the issue about what colors appear in the disk, seems related to the position of the lines in the white background and the direction of spinning;
the white background alternating to the black one provides a rapid sequence of flashes;
lines seen at the beginning of a flash appear (to my eyes) orange, and those at the end of a flash violet.

To tell you the truth, I don't see colors on these (but I do see them on The Toycrafter Benham top).
It could be because they are too small and fast

I believe that they are not Benham disks, because, for to produce the effect efficiently, it seems like there should be elements catching the attention of the eye, (the lines in the Benham disks), especially at the end and/or at the beginning of the white area, (the "flash" area). The designs on those Naef tops do not seem very much based on these principles. 

   

[Iacopo]

As for the Benham disk with the red background, I see bright red in the first ring and dirty red in the other three ones.
It seems like there is a simple superposition of the red color with the colors caused by the spinning disk;
the first ring produces orange, which makes the red there in the disk brighter.