Understanding How All Cameras Work
Although the cameras of the twenty-first century are quite sophisticated, the fundamental principles of photography have not changed. The most important concept in photography is this: photography is all about light. It is the action of light on light-sensitive material that creates an image. For example, a photo of an apple is not really a picture of an apple; rather, the image is created by light that is reflected off the surface of the apple.
How Light Creates Photographs
In order to understand the world of digital photography, it helps to understand how cameras create images from light. You will also need to be familiar with some technical terms. By learning a few fundamental concepts, you will be better able to grasp information on digital photo Web sites and in your camera's manual. This understanding will help you take much better pictures and troubleshoot any problems.
Exposure: The term exposure is critical. Light-sensitive material is exposed when light hits that material. An overexposed photograph is one in which there is too much light; an underexposed image is one in which there is too little light. Film or memory cards that contain pictures that have been shot can correctly be called exposed.
Fundamental Camera Design
All cameras contain six basic elements:
Lens: A plastic or glass element that collects light and focuses an image on light-sensitive material. Every lens also has an aperture, which is an adjustable opening that controls the amount of light entering the camera through the lens.
Shutter: A device that can be opened and closed to control how long the film is exposed to light entering the camera.
Light-sensitive material: The medium on which an image is created. The lens and shutter combine to expose the light-sensitive material to register the image. In a film camera the light-sensitive material is film; in a digital camera it is light-sensitive computer chips (image sensors).
Viewfinder: A lens, frame, LCD monitor, or LCD viewfinder that lets the photographer view the picture before it is taken and as it is being taken, either directly through the lens (in single-lens reflex, or SLR, cameras) or through a separate viewfinder (in simple cameras).
Method for removal or transference of photographs: All cameras allow you to remove the images from the camera. In a film camera you take the film out; in a digital camera you can transfer the images to your computer.
Body housing: A light-tight plastic or metal outer casing that contains the camera mechanism.
Film Cameras Versus Digital Cameras
The big difference between film cameras and digital cameras is the way in which they capture an image. A film camera creates an image when light passes through a lens onto film. The film is coated with light-sensitive chemicals that react when light strikes the film, creating an image. In the developing stage, the image reacts with additional chemicals to produce a photograph.
A light meter is also essential to photography but in the past was a separate device. Most photographers used a hand-held light meter, but today it is built into the camera. Most modern cameras have a system for reading the amount of light. This calculation then determines and often sets the lens opening and the shutter speed.
A digital camera also uses light to create images, but it does so with an array of very small light-sensitive computer chips. A chip is composed of rows of tiny light sensors called photosites that capture color and light. These chips are similar to solar cells in which light intensity is converted into an electrical charge.
This charge is then read and translated into a digital format using an analog-to-digital converter. The chips are categorized as either CCD (charge-coupled device) or CMOS (complementary metal oxide semiconductor). The majority of digital cameras made today use CCDs.