# non-"mirror image" mirror images

**URL:** <https://boards.straightdope.com/t/non-mirror-image-mirror-images/262>\
**Category:** Cecil's Columns/Staff Reports\
**Created:** [October 18, 1999, 10:53pm UTC](https://boards.straightdope.com/t/non-mirror-image-mirror-images/262 "1999-10-18T22:53:00Z")\
**Posts on this page:** 12\
**Page:** 1

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**Author:** ![The\_Ryan](https://avatars.discourse-cdn.com/v4/letter/t/7feea3/32.png) [@The\_Ryan](https://boards.straightdope.com/u/The_Ryan)\
**Post date:** [October 18, 1999, 10:53pm UTC](https://boards.straightdope.com/t/non-mirror-image-mirror-images/262/1 "1999-10-18T22:53:00Z")

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[http://www.straightdope.com/classics/a2\_082.html](http://www.straightdope.com/classics/a2_082.html)

> [@](#):
>
> I’m told that somebody has designed a mirror that uses a complex combination of concave and convex surfaces to produce a “right-reading” image–a mirror, in other words, that allows us to see ourselves as others see us. Robert Burns  
> would have been proud.

“Complex”? I have one in my bathroom. All you need is two mirrors at right angles. One reflects you, the other reflects the reflection, creating a “correct” image. Not that any mirror can truly show you how others see you.  
On a related note, I’ve heard that very tiny three dimensional versions (three mirrors all at right angles to each other) are used to direct light in such places as street signs and car lights. Since these mirros end up sending every light ray out in a path parallel to that which it took coming in, any incoming light (such as a headlight) will be reflected right back where it from (such as the car with the headlights) with a rather minor translation.

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**Author:** ![Boris\_B](https://avatars.discourse-cdn.com/v4/letter/b/fbc32d/32.png) [@Boris\_B](https://boards.straightdope.com/u/Boris_B)\
**Post date:** [October 18, 1999, 11:08pm UTC](https://boards.straightdope.com/t/non-mirror-image-mirror-images/262/2 "1999-10-18T23:08:00Z")

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I was gonna point out that mirrors-at-right-angles thing, but I doubted my ability to explain it properly.

We had a bathroom in my old house that was like this; when I was a kid, I used to flap both arms simultaneously to create the illusion I was looking at a mirror-image - then stop flapping one of them. The _wrong one_ would keep flapping! Used to freak me out every time. But then I was kind of a kooky kid.

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**Author:** ![Jomolungma](https://avatars.discourse-cdn.com/v4/letter/j/b2d939/32.png) [@Jomolungma](https://boards.straightdope.com/u/Jomolungma)\
**Post date:** [October 19, 1999, 10:12am UTC](https://boards.straightdope.com/t/non-mirror-image-mirror-images/262/3 "1999-10-19T10:12:00Z")

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Should we ask what sort of “amusements” you’ve graduated to these days, **Boris** , or would that invite admission of prosecutable offenses?

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**Author:** ![rjk](https://avatars.discourse-cdn.com/v4/letter/r/ed655f/32.png) [@rjk](https://boards.straightdope.com/u/rjk)\
**Post date:** [October 19, 1999, 6:28pm UTC](https://boards.straightdope.com/t/non-mirror-image-mirror-images/262/4 "1999-10-19T18:28:00Z")

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## The three-mirrors arrangement is sometimes used for radar reflectors on sailboats. Look for a set of three intersecting disks forming a sphere hanging from the top of the mast.

Bob the Random Expert  
“If we don’t have the answer, we’ll make one up.”

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**Author:** ![Boris\_B](https://avatars.discourse-cdn.com/v4/letter/b/fbc32d/32.png) [@Boris\_B](https://boards.straightdope.com/u/Boris_B)\
**Post date:** [October 19, 1999, 8:26pm UTC](https://boards.straightdope.com/t/non-mirror-image-mirror-images/262/5 "1999-10-19T20:26:00Z")

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No no, you can’t be prosecuted for amputating someone’s arms and reattaching the left one to the right shoulder and vice versa. Practical jokes are never illegal.

At least I don’t think so.

Right?

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**Author:** ![John\_W.Kennedy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_w.kennedy/32/1031_2.png) [@John\_W.Kennedy](https://boards.straightdope.com/u/John_W.Kennedy)\
**Post date:** [October 20, 1999, 2:58pm UTC](https://boards.straightdope.com/t/non-mirror-image-mirror-images/262/6 "1999-10-20T14:58:00Z")

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The inverse-reflection trick is also used for the movie trick of front projection. A half mirror is used to project an image on the same axis as the camera. It reflects off the inverse-reflection background and the camera sees it, but it is lost on the faces and clothing of the actors.

Of course, blue- (or green-) screen methods have generally replaced this, as well as classic rear projection.

* * *

John W. Kennedy  
“Compact is becoming contract; man only earns and pays.”  
– Charles Williams

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**Author:** ![DavidForster](https://avatars.discourse-cdn.com/v4/letter/d/71e660/32.png) [@DavidForster](https://boards.straightdope.com/u/DavidForster)\
**Post date:** [October 20, 1999, 10:26pm UTC](https://boards.straightdope.com/t/non-mirror-image-mirror-images/262/7 "1999-10-20T22:26:00Z")

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JohnW,

Can you give an example of that movie trick? I’m having a hard time imagining it from your brief description.

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**Author:** ![ravenous](https://avatars.discourse-cdn.com/v4/letter/r/4491bb/32.png) [@ravenous](https://boards.straightdope.com/u/ravenous)\
**Post date:** [October 20, 1999, 10:56pm UTC](https://boards.straightdope.com/t/non-mirror-image-mirror-images/262/8 "1999-10-20T22:56:00Z")

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One of my professors claimed to have invented stealth technology. All you have to do is get rid of all the right angles!

Of course I don’t think he’s the only one who thought of that.

Rav

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**Author:** ![John\_W.Kennedy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_w.kennedy/32/1031_2.png) [@John\_W.Kennedy](https://boards.straightdope.com/u/John_W.Kennedy)\
**Post date:** [October 21, 1999, 12:54pm UTC](https://boards.straightdope.com/t/non-mirror-image-mirror-images/262/9 "1999-10-21T12:54:00Z")

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```auto

_____......Screen
..A........Actor
..|........Light both ways
../--P.....Half-mirror, light <-, Projector
..|........Light to camera
..C........Camera

```

## This doesn’t work with a regular screen, only with the inverse-reflection stuff that’s used on road-signs, etc.

John W. Kennedy  
“Compact is becoming contract; man only earns and pays.”  
– Charles Williams

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**Author:** ![John\_W.Kennedy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_w.kennedy/32/1031_2.png) [@John\_W.Kennedy](https://boards.straightdope.com/u/John_W.Kennedy)\
**Post date:** [October 21, 1999, 12:57pm UTC](https://boards.straightdope.com/t/non-mirror-image-mirror-images/262/10 "1999-10-21T12:57:00Z")

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Arrggghhhh! Make that:

```auto

_____......Screen
..A........Actor
..|........Light both ways
..\--P.....Half-mirror, light <-, Projector
..|........Light to camera
..C........Camera

```

* * *

John W. Kennedy  
“Compact is becoming contract; man only earns and pays.”  
– Charles Williams

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**Author:** ![Triskadecamus](https://avatars.discourse-cdn.com/v4/letter/t/b19c9b/32.png) [@Triskadecamus](https://boards.straightdope.com/u/Triskadecamus)\
**Post date:** [October 25, 1999, 4:48am UTC](https://boards.straightdope.com/t/non-mirror-image-mirror-images/262/11 "1999-10-25T04:48:00Z")

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> [@](#):
>
> a mirror, in other words, that allows us to see ourselves as others see us.

Isn’t that called a wife?

Tris

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**Author:** ![GuanoLad](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/guanolad/32/42_2.png) [@GuanoLad](https://boards.straightdope.com/u/GuanoLad)\
**Post date:** [October 25, 1999, 9:03am UTC](https://boards.straightdope.com/t/non-mirror-image-mirror-images/262/12 "1999-10-25T09:03:00Z")

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I was on the train today…

(contemplates ending the message there, just for the hell of it… but nah)

and was surreptitiously looking at the pretty girl across from me. But the odd thing was her reflection on the wall of the train was not in reverse! Left-right-wise, I mean.

The wall of the train was rippled and slightly concave, but only a tiny bit. Somehow that was enough for it to be affected in spoonlike fashion.

It was utterly odd!

(But nice to see two of her beside each other…)

* * *

“Well, roll me in eggs and flour and bake me for forty minutes!”

[The Legend Of PigeonMan](http://www.hotkey.net.au/~guanolad/pigeonman/)