# The optics of the "Bat Signal" **URL:** \ **Category:** Factual Questions\ **Created:** [June 28, 2003, 9:41am UTC](https://boards.straightdope.com/t/the-optics-of-the-bat-signal/184951 "2003-06-28T09:41:13Z")\ **Posts on this page:** 8\ **Page:** 2
**Author:** ![RevRaven](https://avatars.discourse-cdn.com/v4/letter/r/b782af/32.png) [@RevRaven](https://boards.straightdope.com/u/RevRaven)\ **Post date:** [June 30, 2003, 4:57am UTC](https://boards.straightdope.com/t/the-optics-of-the-bat-signal/184951/21 "2003-06-30T04:57:57Z")
In the comics Gordon and Co shined the Bat Signal on both low hanging clouds and the sides of tall buildings. ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [June 30, 2003, 6:22am UTC](https://boards.straightdope.com/t/the-optics-of-the-bat-signal/184951/22 "2003-06-30T06:22:58Z")
Well there was always the red phone… ---
**Author:** ![Uncommon\_Sense](https://avatars.discourse-cdn.com/v4/letter/u/f9ae1b/32.png) [@Uncommon\_Sense](https://boards.straightdope.com/u/Uncommon_Sense)\ **Post date:** [June 30, 2003, 10:49am UTC](https://boards.straightdope.com/t/the-optics-of-the-bat-signal/184951/23 "2003-06-30T10:49:43Z")
> [@](#): > > \*Originally posted by Desmostylus \* > \*\*Why wouldn’t it be real? The website belongs to a company that does laser light shows. Presumably they’d have some difficulties over false and misleading advertising if the photo was a fake. \*\* I believe you, because I`ve seen this too. Is it holographic technology? How to they get the lazer to appear to hit a surface when all there is is sky? We`ve asked this here before but I don`t think a good answer was put forth, imagine that… ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [June 30, 2003, 10:56am UTC](https://boards.straightdope.com/t/the-optics-of-the-bat-signal/184951/24 "2003-06-30T10:56:32Z")
The text accompanying the other photo is: > [@](#): > > This image was created by Paul Rosenberg of CTA lasers. Paul Writes “ **There was a high fog bank mixed with 500-1,000 foot ceiling clouds passing over San Francisco which made a perfect projection screen.** This event, was for the American Airlines Celebrity Ski Classic with stars such as Kenny G, Michael Bolton and Carole King skiing to raise money for charity. The laser was a Pythan by Cambridge Laser Labs, at least 10 watts, probably more, and I used X29, with an X-Y-I set of Selwyn Lissack’s new pd500 optical feedback scanners.” (my bolding) So it wasn’t just sky, they were lucky enough to have the right kind of cloud cover. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [June 30, 2003, 11:52am UTC](https://boards.straightdope.com/t/the-optics-of-the-bat-signal/184951/25 "2003-06-30T11:52:05Z")
> [@](#): > > \*Originally posted by Desmostylus \* > \*\*Why wouldn’t it be real? The website belongs to a company that does laser light shows. Presumably they’d have some difficulties over false and misleading advertising if the photo was a fake. \*\* Sorry, I meant no offense; my reasons for treating it with skepticism were: -The rays leading to it appear completely parallel, rather than appearing from a point source. -It seems to just ‘stop’ in mid-air; I would expect a little bit of penetration behind the main image. The thing just looks like it was done in photoshop or something. But you’re probably right; the rest of the photos on their site look fine - I suppose they just got lucky with the conditions for the logo shot - presumably my reservations are answered by very dense cloud and that we are only shown a very short section of the rays. ---
**Author:** ![Uncommon\_Sense](https://avatars.discourse-cdn.com/v4/letter/u/f9ae1b/32.png) [@Uncommon\_Sense](https://boards.straightdope.com/u/Uncommon_Sense)\ **Post date:** [June 30, 2003, 1:01pm UTC](https://boards.straightdope.com/t/the-optics-of-the-bat-signal/184951/26 "2003-06-30T13:01:44Z")
> [@](#): > > \*Originally posted by Mangetout \* > \*\*Sorry, I meant no offense; my reasons for treating it with skepticism were: > > -The rays leading to it appear completely parallel, rather than appearing from a point source. > -It seems to just ‘stop’ in mid-air; I would expect a little bit of penetration behind the main image. > > The thing just looks like it was done in photoshop or something. > > But you’re probably right; the rest of the photos on their site look fine - I suppose they just got lucky with the conditions for the logo shot - presumably my reservations are answered by very dense cloud and that we are only shown a very short section of the rays. \*\* Not good enough for me though. I`ve seen lazer light shows where different lazers seemed to stop at different points in the sky. If they were using the same cloud bank they would all seem to stop at the same point. Plus the AA logo seems too flat to be using a cloud bank for a "stop". Also, I`m sure the lazer light shows I`ve seen were not always done on a night were there was a conveniently low particle concentration. How would they have formed the AA logo if there wasn`t ANY particle concentration in the lower atmosphere that night? I`m with **mangetout** , you`d think there would be penetration of lazer light beyond the image… ---
**Author:** ![Sock\_Munkey](https://avatars.discourse-cdn.com/v4/letter/s/aeb1de/32.png) [@Sock\_Munkey](https://boards.straightdope.com/u/Sock_Munkey)\ **Post date:** [July 1, 2003, 12:36am UTC](https://boards.straightdope.com/t/the-optics-of-the-bat-signal/184951/27 "2003-07-01T00:36:55Z")
Light penetration would partly depend on the color of the laser. Some frequencies penetrate haze and mist better than others. ---
**Author:** ![SmackFu](https://avatars.discourse-cdn.com/v4/letter/s/53a042/32.png) [@SmackFu](https://boards.straightdope.com/u/SmackFu)\ **Post date:** [July 1, 2003, 2:16am UTC](https://boards.straightdope.com/t/the-optics-of-the-bat-signal/184951/28 "2003-07-01T02:16:25Z")
The cut-out piece of metal you put in front of the spotlight to project a pattern is is called a “gobo”. It works quite a bit better than construction paper. A small spot can put a surprisingly well defined image on a quite distant surface. See, working on the lighting of the high school musical wasn’t completely worthless! [Previous page](https://boards.straightdope.com/t/the-optics-of-the-bat-signal/184951.md?page=1)