APOD: A Triple Sunrise Over Gdansk Bay (2009 Aug 04)

[Nacho]

The reflections don't have to be necesarily produced by a window pane glass. Here's a picture showing several internal reflections between the camera lenses and the film.

The object is a light bulb, that shows an intermittent trace due to the frequency of the electric current. The camera moved during the exposure, leaving not one trace, but several traces because of the repeated reflections between the film, the lenses and filter.
So the multiple images of the Sun can also be produced by internal reflections inside the camera, with no need of a window pane in between.



This picture was taken by my friend, Dante Bissiri.

[bystander]

The reflections don't have to be necesarily produced by a window pane glass. Here's a picture showing several internal reflections between the camera lenses and the film.

The object is a light bulb, that shows an intermittent trace due to the frequency of the electric current. The camera moved during the exposure, leaving not one trace, but several traces because of the repeated reflections between the film, the lenses and filter.

So the multiple images of the Sun can also be produced by internal reflections inside the camera, with no need of a window pane in between.

The effect was seen without a camera.

... the above image is intriguing because a sincere photographer claims the effect was visible to the unaided eye ...

[neufer]

• ---------------------------------------------------------------
  _________ King Henry VI, part III: II, i
  
  King Edward IV (Plantagenet). Dazzle mine eyes, or do I see three suns?
  
  Richard III. Three glorious suns, each one a perfect sun;
  . Not separated with the racking clouds,
  . But sever'd in a pale clear-shining sky.
  . See, see! they join, embrace, and seem to kiss,
  . As if they vow'd some league inviolable:
  . Now are they but one lamp, one light, one sun.
  . In this the heaven figures some event.
  
  King Edward IV (Plantagenet). 'Tis wondrous strange, the like yet never heard of.
  . I think it cites us, brother, to the field,
  . That we, the sons of brave Plantagenet,
  . Each one already blazing by our meeds,
  . Should notwithstanding join our lights together
  . And over-shine the earth as this the world.
  . Whate'er it bodes, henceforward will I bear
  . Upon my target three fair-shining suns.
  ---------------------------------------------------------------

[nablator]

Hello all,

I registered to tell about my experience with a peculiar double glazed window, that does exactly the same trick of triplicating bright lights, unlike any other window I've seen. I believe it actually triplicates (or more) the whole image, but only very bright lights get a visible reflection.



This picture was taken through the window at a nearly normal incidence angle. Unfortunately I could not take a picture at sunrise or sunset, as the (hotel) window was facing a hill. However I believe the effect is exactly the same. The light is a street light, there are two lens flares, the blue and green lights that are irrelevant to this discussion. This window is a recent model, and has curious properties. When the light is seen through the left part of the window pane, the reflections appear on the left. When the light is is seen through the right part of the window pane, the reflections appear on the right. In between, it is possible to set the distance between reflections to any value just by changing the point of view.

This all points at something uncommon in the glass, either not perfectly parallel or variable width.

[Chris Peterson]

This window is a recent model, and has curious properties. When the light is seen through the left part of the window pane, the reflections appear on the left. When the light is is seen through the right part of the window pane, the reflections appear on the right. In between, it is possible to set the distance between reflections to any value just by changing the point of view.

This is not peculiar at all. It is the normal and expected behavior for any double paned window. In order to not exhibit this behavior, the window would need to be made with optically flat glass, which no commercial window is.

Any double paned window also produces an infinite number of internal reflections, and examples have been given where more than two are seen. Two is what is most commonly observed simply because by the third reflection, there is so little light that even with the Sun as the source, the reflection is typically below the threshold of easy visibility.

[nablator]

This is not peculiar at all. It is the normal and expected behavior for any double paned window. In order to not exhibit this behavior, the window would need to be made with optically flat glass, which no commercial window is.

Yes but the magnitude of the effect, especially at near normal incidence angle, is rather uncommon, I think. I have been unable to find another window (at my home and office) to duplicate the effect. If someone has, was the picture posted here ?

[Chris Peterson]

Yes but the magnitude of the effect, especially at near normal incidence angle, is rather uncommon, I think. I have been unable to find another window (at my home and office) to duplicate the effect. If someone has, was the picture posted here ?

Yes, similar images were presented elsewhere in this (rather long) discussion. And the distance between the internal reflections is independent of the incidence angle, so that's not an issue.

[DinK]

Yes but the magnitude of the effect, especially at near normal incidence angle, is rather uncommon, I think. I have been unable to find another window (at my home and office) to duplicate the effect. If someone has, was the picture posted here ?

I didn't post a picture, but I have a pretty ordinary sliding glass door that produces the effect just fine. I didn't even try it with any of my windows. It only took a basic flashlight sitting on a table in the house, viewed from outside the door, to see the effect.

We were already through this but the magnitude and direction of the effect has to do with how parallel (or not) the panes are and has pretty much nothing to do with the incidence angle you mention. Furthermore since the panes aren't uniform, that means the angle between them changes all over the face of the window/door, so even at a fixed viewing angle the effect will change both magnitude and direction just by looking through different parts of the glass. This was especially easy for me to see as my door could slide back and forth while I remained still.

[green1]

I am surprised. If this is simply a sunrise viewed through insulated glass, it should be a commonly viewed phenomenon, given the proliferation of insulated windows in our world. Since this discussion started there have been many sunrises and sunsets, yet not one (natural) photo showing this kind of optical effect. Given the number of people posting, there should be someone with either an eastern or western exposure that would yield similar effects every clear day.
Those who vociferously insist that this is not a natural effect (dependent on a specific rare combination of factors) give little regard for the individual who took the photo. I believe she is an adult who has seen a lot of sunrises, most of them probably through windows, Why was she surprised to see this effect if it was so common?
To those of you who think this is an optical effect in insulated glass I issue a challenge: duplicate the photo without photoshopping it. (In other words; Put up or shut up".)

[Chris Peterson]

Those who vociferously insist that this is not a natural effect (dependent on a specific rare combination of factors) give little regard for the individual who took the photo. I believe she is an adult who has seen a lot of sunrises, most of them probably through windows, Why was she surprised to see this effect if it was so common?
To those of you who think this is an optical effect in insulated glass I issue a challenge: duplicate the photo without photoshopping it. (In other words; Put up or shut up".)

This matter was settled long ago. The image is a reflection from double paned window glass. This is supported by optical theory, by multiple posted images showing both natural and artificial light sources doing the same thing, and by the later comments of the photographer regarding the conditions under which she took the picture. There is essentially zero doubt about why the image looks the way it does. There's no need for anybody to waste time duplicating work that has already been done. (BTW, precisely duplicating it would be nearly impossible, even from the same room where the original image was taken. The tiniest surface differences from one window to another will radically change the direction and orientation of the internal reflections. What makes this image fairly unusual is that the window pane properties were just right to produce an ordered double reflection, undistorted and in line with the primary image. That's probably also why the photographer took particular notice that morning.)

[DonJones]

I have been enjoying this thread for about a day. For the ray tracers who have tried splitting a single ray – you have missed something. The only point the reflected ray and the directly transmitted ray have in common is the point of interception by eye or camera. I have a non-parallel double glazed window in my bedroom. It is bowed out on the outer pane and bowed in on the inner pane. (The glass was produced and sealed at low altitude and shipped to me in the mountains) Every night I see the light on top of a radio tower about a quarter mile away with its internally reflected shadow self. I can see the reflected image on the left, on the right, above or below the directly transmitted image simply by moving my head a few inches in the direction which I want the reflected image to move.

I suspect that the thread is closed by now judging by the previous date. Drat! I assume by now that the moderator has agreed that meteorological and camera issues – aren’t.

[DavidLeodis]

At the end of the explanation to the APOD it states "If the discussion converges, the consensus will be posted here at a later date". As nothing has yet been added I assume it has been decided that there has been no such consensus. <<< I've just found that in the "View more smilies" link.

[RavenKnight]

If the image is visible to the naked eye, andd I have no reason to believe otherwise, I believe the image is created by the sun's light & image reflecting off Gdannsk Bay and the apparent fog or precipitation in the lower atmosphere reflecting the image back. If the image is examined under a microscopic lens I believe you may find that the image may be reflected infininely as though two reflective surfaces mirror a image whithin each other infinitely.

[geckzilla]

Locking this thread -- Chris said it better than I could:

This matter was settled long ago. The image is a reflection from double paned window glass. This is supported by optical theory, by multiple posted images showing both natural and artificial light sources doing the same thing, and by the later comments of the photographer regarding the conditions under which she took the picture. There is essentially zero doubt about why the image looks the way it does. There's no need for anybody to waste time duplicating work that has already been done. (BTW, precisely duplicating it would be nearly impossible, even from the same room where the original image was taken. The tiniest surface differences from one window to another will radically change the direction and orientation of the internal reflections. What makes this image fairly unusual is that the window pane properties were just right to produce an ordered double reflection, undistorted and in line with the primary image. That's probably also why the photographer took particular notice that morning.)