# Crystal Ball effect using monitor



## Theater (Jul 6, 2013)

Hello everyone!

I have been tasked with making a crystal ball for my theatre's production of The Wizard of Oz. We need it to be able to display prerecorded video for Aunt Em's appearance. This is the setup I was thinking of building... do you think it will work or do you have any other suggestions? Thank you so much!

Tommy


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## mozsey (Jul 6, 2013)

Theater said:


> Hello everyone!
> 
> I have been tasked with making a crystal ball for my theatre's production of The Wizard of Oz. We need it to be able to display prerecorded video for Aunt Em's appearance. This is the setup I was thinking of building... do you think it will work or do you have any other suggestions? Thank you so much!
> 
> Tommy


In my opinion, I think it's a great way of getting the job done. As long as it's slid on stage straight and not rotating in any way as to not reveal the effect. Have you considered sight lines for people higher up in the house if your house is raked?


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## Theater (Jul 6, 2013)

mozsey said:


> I Have you considered sight lines for people higher up in the house if your house is raked?


 Thankfully our house is only slightly raked and we don't have a mezzanine. 

I kind of designed this to be similar to a teleprompter. I will post pictures when built. Thanks for your response! 

Tommy


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## JohnD (Jul 7, 2013)

You might consider sourcing a front surface mirror (also called first surface mirror). They are used for quality kaleidoscopes so stained glass suppliers may have them. They are also used in rear projection TV's and I have seen some of these older behemoths heading to the landfill so you may find someone to gift you with one.


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## Theater (Jul 7, 2013)

Thanks for the advice! I'll definitely keep that in mind when sourcing materials for this. This is a good excuse to tear something apart 

Thanks again!
Tommy


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## Les (Jul 7, 2013)

There are all kinds of cool things in projection tv's including projection lenses (which may even be useful for this project) and that big micro fresnel lens that makes up the screen -- makes a good [-]deathray[/-] solar oven.


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## tladuke (Jul 8, 2013)

Tommy

I think you are on the right track but you may want to consider the virtual image position. In your configuration, the image of Aunti Em will actually appear behind the ball. You have drawn a classic Peppers Ghost configuration. If the mirror is at 45 degrees, the reflected image from the monitor will appear along the bottom edge of your mirror, putting the virtual image very far back.

Wikipedia has a great primer on this illusion called Peppers Ghost. There are several different ways to configure this so that it works in this confined space. You are also not limited to a mirror solution. You could replace the monitor with a small 100 lumen PICO class projector and rear project on a film inside the ball. This would create an image inside the ball and the ball could be round. Transparent projection screen material such as Dilad Welcome - Dilad Screens  would make a great transparent image in a small space. The PICO projector would fit nicely under the table. 

Let us know how this turns out, it sounds like a great illusion.

Tom LaDuke
Walt Disney Imagineering


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## alyx92 (Jul 8, 2013)

A great example of what I think you're going for is in the American Adventure in Epcot. They've recently added these lanterns with a variation of the design we've been talking about here.

Here's a video:

Imagination Lantern video from the Kinsey exhibit at Epcot 3-8-13 - YouTube

In this version, there appears to be a piece of glass running straight up the center of the lantern and a small screen is housed at an angle above or below the center of the lantern. Still you would probably want to test to make sure your extreme sightlines house left and house right still get the illusion.


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## ruinexplorer (Jul 13, 2013)

Question, do you intend to have the image be on the surface of the crystal ball or do you want it to appear inside?


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## Theater (Jul 13, 2013)

Thanks everyone for your responses! I guess the image is going to appear inside the ball with the original configuration I pictured. I do have a rather cheap projector I got from Bed Bath and Beyond a few years ago, so that may be an option for this... Thanks so much for your responses. I'll post pictures as soon as this is built. I'm going to spend some time on this over the weekend and during the coming week. 

Thanks again!
Tommy


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## techietim (Aug 4, 2013)

This is awesome!

I'd love to see some photos if/when you get round to getting it built!


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