Video feedback is an interesting phenomenon. Take a video camera and plug it into the TV so it shows what the video camera is filming. Then point the camera at the screen. You will then see repeating patterns that create some unique fractal like patterns. This also works with a webcam on the PC if you point the webcam at the screen area that shows what it is filming, but using a real video camera an TV gives much more interesting results.
Here are a few examples of real video feedback. Depending on the brand of camera and TV you will always get unique results.
I encourage everyone to try real Video Feedback if you have the equipment. In the past I have shown the process to anyone with a camera and the right cables to connect the camera to their TV, and they all have had a wow moment when seeing it for the first time.
If you are interested in trying it for real, here are a few tips;
1. Do it in a dark room or with minimal lighting. Trying it during daylight seems to cause a “white out” as there is too much background light that bleeds into the image and is amplified repeatedly.
2. Turn the camera upside down (ie 180 degress to the TV image it is filming) as this gives better patterns usually.
3. If your camera has effects for inverting the image, use it. Try all the various filters the camera provides. Adjust the contrast and brightness. Play with all the available controls. Also adjust the TV brightness and contrast.
4. Try slight camera rotations rather than big movements. A nice pattern can be killed with rapid movements of the camera. Same for zooming.
5. If the image dies out, flicking the room lights on and off momentarily can get it working again. Alternatively putting a lighter or candle flame between the camera and TV can get a dead display running again.
A few years back I got into trying to attempt to simulate Video Feedback in software. The results so far are promising. Here is a sample movie of the results.
For more info about the simulation techniques used, see my Video Feedback page.