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Topic: It's All done wiv mirrors laddie
Message: Posted by: RangeCowboy (Mar 9, 2002 02:58AM)
No big secrets given away here I think.

I have been looking at an old Abbott's Illusion using a couple of plane mirrors. So of course I thought to myself - I can do better - and dreamed up my own box illusion and put it down on paper, plan view, elevation end-elevation etc. and it looked great.

Then I built two cardboard models (A) simple, (B) more complicated. Both made to about 1/4 scale and it used four mirrors which are the acrylic plastic type you see in bathroom fittings these days. The end result while logically technically correct had two major flaws.

First, there is a visual pathway which negotiates (A) two and (B) four mirrors in my designs [Design A is the simple Design B is complex] and the problem is the reflectance of the mirrors. I'm guessing 98% or so and by the time the 4 mirror plan is viewed by the spectator the image is seen as quite obviously darker than the surroundings.

0.98 x 0.98 x 0.98 x 0.98 = 0.92 so again guessing, it's about 8%-10% darker

So my question is - do the big illusion guys use surface silvered mirrors or what? I have read about pure nickel plated mirrors used by Houdini.

Secondly and it was unexpected, the very slight curvature introduced by the acrylic mirror being hand-glued in place was again amplified through the two or four sets in the A and B test models, and the spectators view was akin to visiting the Hall of Mirrors at the fairground. I could quite definitely discern that the "open space" in my illusion was going to fool nobody.

Quite a setback for my first attempt at making my own box illusion and I wonder if anyone has any tips?

I resorted to placing a flashing warning light behind the aperture and the flashing distracts ones view or perception of the darker image but that's a klutz solution.
Message: Posted by: Steve Brooks (Mar 9, 2002 03:25AM)
While I normally do only close-up, I have done smaller illusions, and do own a couple myself (Sword box, Sub-trunk, Mirror box, etc).

Mirrors and reflections are an interesting thing to work with. On the one hand, it's fairly easy to fool the human eye. On the other hand, the eye is used to seeing the world a certain way, and anything that looks odd will be spotted fairly quickly.

Some things to think about when using an illusion that might make use of a mirror are:

1) Lighting. Where will the lights be?
Will they reflect off the mirror itself?

Things on stage under lights look much different than they do under regular lighting. As an example, I found out very quickly that using swords made out of aluminum look much better that swords using real chrome. Why? The aluminum shines very nicely under stage lights. The chrome is too shiney, and reflects the lights way too much.

2) Mirrors. I have found that so-called household mirrors work very well, but must be clean. Any dirt, smudges or dust, and the cat's out of the bag!

A simple mirror box makes a good example. Look at one up close. Even knowing the mirror is there does not reveal the secret, unless the mirror is dirty.

3) Patterns. Painting is often used to fool the eye, such as making an area seem smaller, etc. But say you are using a 45 degree mirror, then it's important to exagerate a pattern, so as to guide the eye into the illusion, the mirror only serving as the springboard so to speak.

4) Loss of image. You spoke of four seperate mirrors, be careful using so many. As light hits one mirror and reflects into another, and so on. Each reflection is a copy of the previous, and will lose resolution.

Think of it this way. I tape a television show, which looks okay. Now I copy that tape, and the image no longer looks sharp. Now I copy the copy, and the image quickly starts falling apart. Yikes!

While I have not exposed any major secrets, I do hope to have been of some help.
Good luck on your project, and let us know how it turns out!
:bwink: :bigdance:
Message: Posted by: RangeCowboy (Mar 9, 2002 03:50AM)

Can you confirm without giving away secrets of the inner sanctum e.g. Sword Box

Surface or Backcoated?

Boxers or Briefs?

I have two chunks of block acrylic plastic
6x8x3" thick and four mirrors like two v's sitting on top of each other

--- V ----line of sight
--- V ----

Looking for some salvation.
Message: Posted by: Steve Brooks (Mar 9, 2002 03:59AM)
You would ask that. My stuff is not where I can easily check. Hmmmm...as I recall, back coated. Does this help? :hamburger:
Message: Posted by: Thomas Wayne (Mar 9, 2002 09:31AM)
On 2002-03-09 04:50, RangeCowboy wrote:
I have two chunks of block acrylic plastic
6x8x3" thick and four mirrors like two v's sitting on top of each other

--- V ----line of sight
--- V ----

Looking for some salvation.


I have built a number of experimental versions of EXACTLY the principle you are describing. there are a couple of things you should know:

1) This idea is already protected by at least one patent. If you are just experimenting for your own use you'll be fine, but if you intend to market your idea you may be wasting your time AND risking costly litigation.

2) The pathway that light (and therefore any sight picture) must take is much longer than a straight shot through your "opening".

Therefore, objects seen through this opening will appear much farther away and much smaller. Background patterns will not match up properly, and vertical sections (poles, human legs, etc.) will appear to distort differently than horizontal ones.

As for mirrors, the highest quality GLASS mirrors are your best bet, but even they are not 100% efficient and the multiple reflections consume brightness at a seemingly exponential rate.

Frankly, the principle is intriguing, but, in practice, it has very limited applications.

Thomas Wayne
Message: Posted by: Magicduck (Mar 12, 2002 01:19AM)
I believe that mirrors are best if the situation is simple... one mirror or two.
I use them for a number of effects, however, rarely is one more elaborate than removing a load from above a mirror or those V mirrors opening out to the sides. One marketed effect, flaming head chest, is a more complex than usual box and can be effective but only with the correct backdrop... such as a stage curtain.

In the right situation the head vanishes quite nicely. But if the helper, with the box on, is standing in front of a wall picture or somthing very specific, the images do not line up and the trick would be a giveaway.

I have also found it is best to use patterns when decorating the walls or sides the mirrors reflect, which are not straight lines. I once built a small "tent in the desert" with neat looking vertical striped cloth. Between trying to get the cloth on straight, and the mirrors being just enough off from straight on the hinges it was a big problem. I ended up putting new cloth on... easier than rearranging mirrors that mechanically worked great and looked great for other fabric.

I have yet to find any use for the plastic mirrors that was not better served with glass. I tried a plastic one in a duckbucket once and found two things
(1) darker inside
(2) slight warp
which made the inside look weird. Sounds a lot like your problems, eh?

Message: Posted by: RangeCowboy (Mar 17, 2002 08:29PM)
Thanks MagicDuck,

That kinda confirms the culprit.
The transmission of light off the silvering and through the acrylic plastic must be a lower percentage than glass, and you comment on the warp when mounted anything but vertical, causing a very slight sag and on a large sheet becoming a concave/convex like the mirrors you see on blind corners.

I guess one way is to glue the mirror to a frame which is stiff and cross-membered.

When Penn and Teller do their mirror work, I hear they spend hours setting up the mirrors with tweaking screw mechanisms to adjust angles.

That's a lot to expect for a roll-on illusion that gets packed in a case after the performance. I'm going to try using a fairly fast-setting two part adhesive like Araldite to float in the mirror against the supports and then hope it hardens OK. I'll report my findings. And until then avoid the use or need for multi-part mirror tricks.

'If you can't solve the problem - change the problem'