Deceptive Shadows

About this video

Pinhole camera trickery.

Veritasium's  Derek Muller visits the sunny Australian coast to ask members of the public to predict the outcome of his simple pinhole experiments.

If you shine sunlight through a hole in a piece of paper, it will project an image of the Sun on the surface behind. The same image of a Sun will appear whether the hole is large or small, square or triangular. 

So, why does the size and shape of a hole have little effect on the image it projects?

When light is forced to pass through a pinhole, it forms an inverted (upside down) image of what it sees. Because light travels in straight lines, the light reflecting off the top of the object will create a point of light at the bottom of the image, and light from the bottom of the object will create a point of light at the top of the image.  

What we see is an (upside down) image of the sun, not a projection of the shape of the pinhole. By changing the size and shape of the pinhole, you can only change the focus of the image. The smaller the hole, the sharper the image.