Natural magnification(special circumstances)

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Discussion Overview

The discussion revolves around the phenomenon of natural magnification observed through mesh screens and reflective surfaces, specifically focusing on the appearance of Moire patterns and related optical effects. Participants explore the underlying mechanisms and implications of these visual phenomena.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant describes observing a magnified virtual image of mesh screens from a distance, suggesting a connection to interference or the "pin-hole" effect.
  • Another participant identifies the observed phenomenon as Moire patterns, explaining it through interference patterns and spatial aliasing in signal processing.
  • A later reply humorously references Moire patterns in other contexts, such as through fishnet tights, while also questioning their relation to the appearance of magnetic field lines seen around bright light reflections.
  • Further discussion includes a participant's personal experience with changes in visual perception due to windshield conditions, suggesting that scratches may affect light interference.
  • Another participant reflects on their past observations of the effect, indicating that they have not encountered it recently and plan to investigate further.

Areas of Agreement / Disagreement

Participants generally agree on the identification of Moire patterns as a key aspect of the observed phenomena, but there are varying interpretations and additional questions regarding related effects, such as those involving reflections and light interference. The discussion remains unresolved regarding the broader implications of these observations.

Contextual Notes

The discussion includes personal anecdotes and subjective experiences, which may introduce variability in the observations described. There is also a lack of consensus on the relationship between Moire patterns and other optical effects mentioned.

Who May Find This Useful

Individuals interested in optics, visual phenomena, and the interplay between light and materials may find this discussion relevant.

pallidin
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Hi everyone,

Say, I was wondering if you could explain something to me.
I have two examples to share:

1) I drive by several enclosed bus stops on my way to work. The enclosure consists of a solid roof, but the sides are a metal mesh screen with circular holes less than the diameter of my pinky.
Anyway, as I'm approaching there is one screen facing me and another behind it, say 6-feet from the first mesh.
I can see images of the circular mesh as if it were magnified 500-1000 times!
From my distance, say 100 feet, I can not see the actual circular holes, but I can see, quite clearly, a hugely magnified virtual image.

2) Outside my house right now(which prompted my Q) is a maintenance pickup truck with a diamond shape metal mesh enclosure surrounding the top sides of the pickup bed.
From my distance I can not see the individual diamond mesh, but I see the hugely magnified virtual image. Walking towards it, the mesh is indeed diamond shaped mesh. Again, as in 1), there is a second similar mesh behind it on the other side of the pickup bed.

I assume this has something to do with either interference or the "pin-hole" effect.

Any thoughts?
Thanks...

Edit: sorry for all the edits. Spelling typos.
 
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Science news on Phys.org
You are seeing Moire patterns and they are well-studied. They can be understood in many equivalent ways--interference patterns (as you suggested) are a good approach. It can also be understood in a signal processing context as spatial aliasing due to undersampling (violation of the Shannon sampling theorem). There are many Google sites covering these. Please come back if you have further questions!
 
Thanks Marcus. Moire patterns!
I knew there was an explanation and you nailed it.
Cheers!
 
You get some interesting Moire patterns through fishnet tights. You may also get a smack.
 
sophiecentaur said:
You get some interesting Moire patterns through fishnet tights. You may also get a smack.

Right, I think I should be most careful as to NOT examine that. :biggrin:
 
pallidin said:
Right, I think I should be most careful as to NOT examine that. :biggrin:

chicken ! --- where's your sense of adventure ? ;) haha


But seriously for a moment... does that (Moire patterns) also explain the appearance of what looks like the classical magnetic field lines (bar magnet under paper with iron filings sprinkled on top) that you see around a bright point of light reflecting off say a car's chrome bumper bar etc ?

For many many years, that phenomena has always baffled/intrigued me for an explanation, or am I the only one with weird super vision ;) haha

Dave
 
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davenn said:
chicken ! --- where's your sense of adventure ? ;) haha


But seriously for a moment... does that (Moire patterns) also explain the appearance of what looks like the classical magnetic field lines (bar magnet under paper with iron filings sprinkled on top) that you see around a bright point of light reflecting off say a car's chrome bumper bar etc ?

For many many years, that phenomena has always baffled/intrigued me for an explanation, or am I the only one with weird super vision ;) haha

Dave

Dave, are you seeing this through your windshield or seeing it directly through open air?

Edit: The reason I'm asking is that, a few years ago I bought a newer car with a "perfect" windshield.
In all lighting conditions my viewing was great.

That following winter I used, many times, a scraper to get ice off the windshield(apparently the previous owner had a garage)
Anyway, I noticed a BIG difference when point-light sources came through the windshield after winter.

I assume I incurred multiple scratches on the windshield using my scraper; causing some kind of light interferance.

With my now "newer" car, I no longer use a scraper at all. I just take the time to heat the car up and defrost the windows.
 
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good question, its been a while since I saw the effect, prob just not in the right place at the right time.
But from vaguest (sp?) memory being inside a car was irrelevant ... I "thought" it was something I noticed whenever I happened to spy the sun shining off a bright reflective (most likely curved) surface.

I will have to look out for it again and come back with some informed comments :)

Dave
 

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