# B Can someone explain this projection distortion effect

1. Sep 20, 2016

### jwilliams77

Hi,
Sorry this is an unusual thread and question, but I figured people here might be able to explain the physics of what is going on in this image

I came across a few images of an underground music club in Berlin where an image of stained glass art you would find in a church is being projected behind a band playing and (I think) it is purposefully distorted by being projected at an unusual angle against a wall to create an abstract/psychedelic "stretching" pattern.

Here is where I'm confused. I'm not sure if I'm massively over thinking this, and this is simply what happens to a projected image when it hits a wall right next to it, and that is what causes it to "stretch", or if there is more going on here, like:

A) Someone placed a small mirror next to the projector/bulb to create a "prism" effect (like the Dark Side of the Moon rainbow)

or

b) The image of the stained glass art is originally stretched/distorted by whoever created it in Photoshop or something, and the projector has little to do with the "stretching" effect

I'm asking because I really like the effect of the image being stretched to look like it's about the jump to "light speed" like in Star Wars, and I'd like to recreate this effect to see what patterns could be generated with other images, and I'm generally curious about the physics involved in the distortion of light/images.

Is this simply what happens when a projected image hits a wall like that? If you were projecting any movie at this angle against a wall, would the actors faces get stretched into "light speed" like this? Or do you think the art/image itself was originally made this way and it has nothing to do with the projector? Or something else?

This is probably the strangest thread ever posted to this forum, and again sorry if it's too off topic

2. Sep 20, 2016

### davenn

simply ... Yes !

note in pic 1 the image on the end wall is normal because the projector is perpendicular to that wall ( at 90 deg)

note in your pic's 2 and 3 that the projector can be seen and the angle between it and the wall is very small ... almost parallel to each other

you could do the same thing at home with a torch ( flashlight) and see the same effect

Dave

3. Sep 20, 2016

### jwilliams77

Thank you!

4. Sep 21, 2016

### A.T.

The only strange thing here is that you are old enough to get into clubs, but have never noticed this effect so far.

5. Sep 21, 2016

### Khashishi

It's just geometric optics. You can treat light as being cast as a bunch of rays from the projector. Wherever the ray intersects the wall gets illuminated.

6. Sep 23, 2016

### mister mishka

Which club in Berlin was this? I at the moment create my own visual films, aiming for places like Griessmuehle or Sisyphus. So visual films to go along with house and techno music. You can do a 3d projection mapping / video manipulation with software like Resolume, but yeah I like the more hands on approach and work with creating visuals from playing with light / live video manipulation (polarizers, diffraction gratings, prisms, lasers, mirrors, surfaces, video feedback delays, etc). If you are interested you can check out some of my work on https://vimeo.com/mistermishka