How does the pinhole camera use light?

A camera admits light through an opening to expose an image on film. To get a sharp image if the light is not bright, you need a large hole, but the larger the hole, the more blurred (unfocused) is the image. But if you make the hole as small as a pinhole (like poking a pin through cardboard), you will get a focused picture if the light outside is bright enough. If the hole is any larger than that, you need to put a lens in the hole to focus the light. The larger the hole, the dimmer is the scene that you can capture, but the larger the lens, the more complicated is the optics (the physical design of the glass lenses, using several lenses in a row).