Mirror phenomenon

[aliasz]

Main Question or Discussion Point

Follow up a former thread, about concentric halo`s around the eyes, in a foggy bathroom mirror.
I made an example picture of what was observed.
But i dont know what causes the phenomena

 

[berkeman]

Follow up a former thread, about concentric halo`s around the eyes, in a foggy bathroom mirror.
I made an example picture of what was observed.
But i dont know what causes the phenomena
View attachment 114858

Welcome to the PF.

So you can use Photoshop. Can you use Google Images or some other search tool to find real images of what you are asking about?

 

[aliasz]

hi, no i am sorry i couldnt find any real images on this subject, so for now i made an observation and a mockup in photoshop.
maybe i can take a photo of it when it happens. but i dont think my camera on my phone will capture this effect/phenomena on photo
due to poor lighting conditions.

 

[aliasz]

and my question about the phenomena is the same as this user "see older thread" has questioned here, only i made an example of the effect
https://www.physicsforums.com/threads/mirror-phenomenon.432734/

 

[jedishrfu]

It may be related to aberration. In telescopes, you'd see rings in the field of view:

https://en.m.wikipedia.org/wiki/Spherical_aberration

 

[Daz156]

Follow up a former thread, about concentric halo`s around the eyes, in a foggy bathroom mirror.
I made an example picture of what was observed.
But i dont know what causes the phenomena
View attachment 114858

I joined this forum today specifically because I had this happen to me this morning. i had dried off and turned round to look into mirror only to be greeted by the above- i likened it to two empty glasses that had been filled with milk. My gf thought I was going nuts, this eve she text me her google search and that lead me hear...

 

[Daz156]

PS I tried taking pictures, but I assume that as the camera comes from a different angle it does not catch it.

it is clearly the mirror and condensation combined, amplifying the whites around the eyes to give the effect.

 

[jedishrfu]

Check the spherical aberration link. There are some images toward the end of the article that look like what you saw.

https://en.m.wikipedia.org/wiki/Spherical_aberration

 

[Daz156]

Looks like positive spherical aberration (bottom row of table), the column to the far left shows defocusing toward the inside, and that looks like the bright white rings round my eyes I witnessed. I note it was more pronounced the closer I got to the mirror, looking like a set of lit up bright white “John Lennon” glasses

thank you for the link, seems to be the answer.

 

[jedishrfu]

Yeah, this optical phenomena can be a bane for amateur astronomers who try to get the most out of their reflector telescopes. It occurs in all sorts of other optical instruments too.

 

[DaveC426913]

I'm a little confused. What specifically about the foggy mirror would result in spherical aberration? SA is about focus, right? I see it looks the same, but is it the same phenomenon?

My first thought was that it was more akin to (though not the same as) circular rainbows:

or the halo around street lights in rain/fog/snow:

These phenomena are more about reflections from a halo of water around a central point.

 

[jedishrfu]

It could be related to your eyes.

 

[Cybertib]

Isn't it simply the Fourier transform of the distribution of nano-droplets induced by the fog? If size distribution of droplets is quite uniform. Main weakness of this idea is: the scattering to far field has to be with a infinite focus point. Sounds contradictory.

Open to comments! :)

Best,
Thibault

 

[sophiecentaur]

Follow up a former thread, about concentric halo`s around the eyes, in a foggy bathroom mirror.
I made an example picture of what was observed.
But i dont know what causes the phenomena

I can't see how people would think in terms of SA because why would that only be visible with a fogged mirror? Any scope with that level of aberration would go in the bin.
I think your sketch(?) is suspect if you can't produce the same effect with a camera. If there is not enough light then take a lamp into the bathroom or take a mirror outside and boil a kettle near it. You need to experiment a bit and try to reproduce a genuine picture. That would establish some credibility.
There are many different 'halo' effects when light passes through water droplets or ice crystals. This looks like a version of that effect. Spherical / Hemispherical water drops on the glass would give circular symmetry. Try cleaning off half the mirror and see what happens.

 

[sophiecentaur]

Main weakness of this idea is: the scattering to far field has to be with a infinite focus point.

That doesn't follow. You will get a diffraction pattern at all distances and actually the distance from mirror to eye is pretty much ∞ in comparison to drop size and wavelength.

 

[Samimnot]

Here is some information that may shed light on the subject. It lies in the realm of anatomy. Have you ever witnessed the reflection from a cat's eye at night? It is due to the micro-spherical shape of each eye cell, as well as a macro-spherical shape of the inner eye-cavity. Light which enters the eye, scatters in a spherical pattern, towards the light source/observer because of both, the micro and macro structures of the eye. The former is like reflective beads on a projector screen or road paint. The second is like the secondary mirror on a reflector-type telescope. In a foggy room, this complex light-scattering effect would tend to produce a uniform glow emanating from the pupil, almost like a hologram of the inner eye, as opposed to a point-source. This hologram-like light pattern can illuminate the inner eye, and the area of fog around the pupil, from the perspective of the viewer or camera. In humans, this reflection is attenuated by retinal pigments. But if the incident light is strong enough, or the person has very fair complexion, eye-reflections can be bright enough to see, and bright enough to illuminate the area around the eye.

 

[sophiecentaur]

Light which enters the eye, scatters in a spherical pattern, towards the light source/observer

At night, a bright, localised source will form a point image on the retina that is intense. In human eyes, this intense spot will be bright red (blood colour) and the eye lens will focus this image at 'infinity' in the direction of the original source (reciprocal optics). That accounts for RedEye from flash photographs when the flash gun is near the camera axis and can be reduced by having the flashgun off axis. (Bad shadows can result from this so you can't win)

Cats use the reflective layer behind the light sensitive cells to make the light pass back through them, which will double the received signal and both increase the light level back at the source and lose the red colour. I can't find a diagram of the details of the reflective layer but you are implying that, behind each cell there is a curved reflector which provides a bigger gathering area than the cell itself. That's smart!! I guess it may affect the cell spacing and hence, the resolving power of a cat's eye. But, hell, they don't need to read an eye test chart to spot prey within catching distance.