Talk:Haidinger's brush

message: I think that the simulation image is physically inaccurate - most (all?) LCD screens are setup with the polarization axis at 45 degrees to the vertical (though which side of vertical varies between screens).  This is also true for pocket calculators.  Yet the simulation picture shows the polarization axis aligned horizontally (the blue bits give the direction of the E field polarization). A.C. Norman (talk) 20:19, 17 March 2009 (UTC)
thread_title:  Simulation Picture 

message: I have been able to see this effect for some time now, both in the sky and on LCD displays, after an article about it appeared in Sky and Telescope magazine.  I am also an "expert" video observer.  Even on my properly-adjusted display, the "Simulated appearance of a computer screen" is impossible to discern -- the actual effect is, in fact, more easily visible.  For that reason, I recommend removing it or exaggerating it to become more visible. algocu (talk) 22:49, 14 February 2008 (UTC)
thread_title:  Sublety not effective 

message: I think that a very important thing to point out is that H's brush is mainly due to xantophylla visual pigment. Human vision in based upon four visual pigments: lutein (viz xantophylla), heomoglobine, ferrohemoglobine and ferrihemoglobine. The first one has three particular features
we are interested in:
1) absorbs in the blue range of spectrum
2) Has a very anisotropical shape (it's a rod...); radiation stimulates both electronic states and
   molecular vibrational states, which are mainly disposed along with the molecule direction. That
   means that xantophylla is sensitive to the polarization of the light.
3) Xantophylla pigments tend to be parallel to visive nerves; these, because of the fact that fovea    
   is not flat, are almost orthogonal to the fovea in its central part, and nearly parallel in its
   outern region. This means that two different areas of the fovea are mainly sensible to two different degrees of polarization.
Point 1) tells us that H's brush should be visible in the blue/violet spectral range.
If you think we should fix all this, please tell me; I can provide sufficient bibligraphy, too (Raman's peapers about visual perception)--CAPITANEVS (talk) 22:15, 25 April 2008 (UTC)
thread_title: Xantophylla is the responsible of the Brush...

message: I noticed a few errors with the pigment names.
I changed xantopylla to xanthophyll. I think that was what the article meant. If there are any objections it can be easily changed back.
I see a few errors in this sentence:
Haidinger's brush is entirely due to peculiar features of one of the four visual pigments human vision is based on, that is xanthophylls (also known as lutein, the others being hemoglobine, ferrohemoglobine and ferrihemoglobine).
I don't think that xanthophyll pigments are the visual pigments. (maybe their metabolites are).
Hemoglobine (and its erroneous rivals) is not a xanthophyll pigment, nor a visual pigment, it is the oxygen carrying pigment in vertebrate blood.
The xanthophyll pigments are (lutein, zeaxanthin, neoxanthin, violaxanthin,α- and β-cryptoxanthin).  —Preceding unsigned comment added by Dursty (talk • contribs) 03:01, 28 September 2008 (UTC)
thread_title:  Pigments 

message: My understanding of this phenomenon is that the effect should be parallel to the direction of polarization for linearly polarized light, but should be fixed to the viewer's eye for circularly polarized light. For this reason, in the case of an LCD monitor you should not expect the effect to "rotate" when you tilt your head, but rather be fixed to the screen. Can anyone confirm this is correct, and fix the confusion in the article? (I'm not an expert) Meekohi (talk) 05:37, 25 February 2009 (UTC)
thread_title:  Rotating Head 

message: ..."With practice, it is possible to see it in the naturally polarized light of a blue sky. ". 
This is quite true, BUT it needs to be added that the naturally polarized part of the sky is the great circle (or part thereof) that is perpendiculr right angle to the sun. For example, at sunrise/sunset, the polarized part is the meridian.
Old_Wombat (talk) 07:48, 29 September 2011 (UTC)
thread_title:  Seeing it against the sky 

message: Is this supposed to be a joke?  --Doradus (talk) 13:01, 16 July 2012 (UTC)
replies: text: I agree. The incomprehensible vocabulary persists eight years later. An expert is needed to rewrite this section into much simpler prose.Robert P. O'Shea (talk) 13:33, 16 September 2020 (UTC)
thread_title:  Incomprehensible vocabulary 

message: this xkcd item mentions that humans can see polarization and the graphic it uses seems to work pretty well. I wouldn't have found this page without having tried it. EdwardLane (talk) 10:48, 20 August 2012 (UTC)
replies: text: Thanks! But I don't think the "blue-sky sprites" mentioned here are the same as Haidinger's Brush. The page says that they are caused by white blood cells in the retina, but that's not how Haidinger's brush is formed. Kortoso (talk) 21:33, 15 April 2016 (UTC)
thread_title:  xkcd 

message: I was not able to see the Brush no matter how hard I tried, until we went to Questacon (a sort of science museum) in Canberra (ACT, Australia). They have a display there precisely for this purpose - a white screen illuminated by a floodlight in front of which is a rotating polariser. With this apparatus, the Brush is trivially easy to see as it rotates. Most importantly, first and foremost, it confirmed that I COULD see it, and it also gave me an idea of what (angular) size it is, the colours of it, and the expected difficulty of seeing it. After this ... I can now see it very easily.
If you bring up Paintbrush with its default empty white image, and move the mouse cursor to roughly the centre of it, it gives you something to stare at whilst you rotate your head. I have found this background to be very good for seeing the brush.  — Preceding unsigned comment added by 101.161.169.86 (talk) 05:17, 14 August 2016 (UTC)
thread_title:  "How I first saw HB". 

message: When you have two monitors, phones, etc (preferably equal brands), and one of them is rotated 90°, look alternatively to white areas on either one. When your eyes get used to the blue and yellow from looking at one monitor (even if you still can't discern it), looking at the other one duplicates the effect. This is because those areas on your retina which are now slightly desensitized to blue are now seeing "yellow minus blue", and vice-versa. Not only are the colors more prominent, the contrast between the colors is too. --Zom-B (talk) 08:58, 28 September 2016 (UTC)
thread_title:  Double the visibility!