How it works - Thickness & Shape
Fundamental Law: Light travels in a straight line
Observe two pinholes of different thickness. The one on the left is much thicker than the one on the right.
The most obvious difference experienced is the varying angle of coverage. A real concern when using pinhole cameras of extreme wide angle. This effect can be exploited when you want the image to appear circular in the final result.
Another potential problem is the reflectiveness of the inside of the pinhole. The thinner it is the less surface area there is to reflect light, light you don't normally want interfering with your image. This can be exploited when purposely pointed at the sun to get 'flare' images.
Here is an image with mild flare [normal pinhole thickness], caused by reflections of the sun off the pinhole 'sides'.:
|Normal shaped pinhole and resulting image|
|Pinhole stretched in the horizontal dimension and resulting image|
|Pinhole stretched in the vertical dimension and resulting image|
Of course much more exotic shaped pinholes can be produced. All will cause varying degrees of blurring over a normal pinhole.