There are certain kinds of cameras these days that are truly impressive in not only how mechanically simple they are but also in the kinds of pictures they can take.

One such is what's called a pinhole camera, and many folks might be a bit surprised to learn that the basic theory for the camera can be traced back to the 4th century BC, when Greeks such as Aristotle and Euclid both wrote on the principles that would one day lead to the development of the actual camera.

At its most basic, a pinhole camera is extremely simple and doesn't even have a lens, as most other kinds of cameras do. It has an extremely small aperture ("opening," "hole") through which light passes ("light," in the case, meaning the image). It is composed of a light-proof box that has that a single small hole in one side.

What then happens, when a pinhole camera is used, is that light will pass through that hole, where it will be inverted (turned upside down, in effect) and projected on the other side of the box (inside it, of course).

Both cameras with very tiny apertures and the human eye – when it's exposed to bright light – act like pinhole cameras, by the way.

The beauty of this kind of camera is that the smaller the aperture (or hole) is, the sharper will be the image.

Of course, the downside is that the image will also be dimmer due to this effect, so it's always recommended that the size of the hole be one one-hundredth or less of the difference in distance between it and the screen upon which the image is displayed.

A pinhole camera can serve a number of different purposes. For one, when its used with a "charge coupled device" (a CCD semiconductor, upon which the light will be splashed and then converted into an image that can be transmitted or sent via a tiny wire to some receiver media like a monitor) it makes for an outstanding surveillance camera.

The reason this is so is that the tiny, tiny light-proof box, with its equally tiny aperture (pinhole-sized, literally) is paired to an equally-tiny CCD, which can send a high-quality digital image to wherever the camera is programmed to send the image to.

And these cameras are very tiny, which makes them extremely hard to detect in a surveillance situation. If considering using one, keep in mind that some CCD semiconductor image sensors use a lot of power, meaning the camera may not be able to run for very long.

Also, a pinhole camera has no lens, therefore any such camera will depend upon the brightness of the light projected in the viewing area, though a CCD can make good use of available light.

If the lights are turned off, no image will result. If the light conditions keep changing, image quality may suffer greatly.

If they fail to work properly, it's usually because the CCD has drained and the tiny battery powering it needs to be replaced.

Just replace the battery and let it get back to work doing whatever it's being used to do.