It has a lens in the front and a viewing screen in the back with flexible bellows sitting between them. This type of design was founded back in the early days of photography and is still being used today. Though it is simple, this camera is very flexible and it's capabilities are not seen in any other type of camera. The lens produces an inverted image on the ground-glass plate located in the rear of the camera. The image is composed and focuses on this plate. To take an image with this camera you must place the film (emulsion side up) on the plate when taking the exposure. Then under a dark lightless cover remove and replace the film, while placing the exposed film in light-tight casing.

This camera typically uses a sheet of film measuring 4" x 5" or sometimes larger. This size of film allows for great detail and resolution. The camera must be placed on a tripod when taking a picture. It is relatively slow to operate. Ideal applications for this camera are indoor and outdoor portraiture and product advertising.

Viewfinder Camera

These cameras view their subjects through a very small hole that has a simple lens that provides an image of how the final picture will look. The light from the subject, however, travels separately through the lens to the film and through the viewfinder to the eye. Therefore the viewfinder and the camera lens are actually viewing the subject from two different levels resulting in parallax error. What you see in these cameras is not always exactly what you wanted.

The parallax error is not the greatest disadvantage to using this type of camera. Most of these cameras do not support special lens. These cameras are using quite inexpensive and today they even make disposable versions.

Single-Lens Reflex Camera

These types of cameras are probably the most widely used by professional photographers. Light taken by these cameras is seen directly through the same lens that takes the image final picture. Light from the lens is reflected by a mirror inside the camera upward into the viewing system.

When the photographer presses the shutter release mechanism, the mirror quickly swings up and allows for light to pass through the shutter and expose the film and quickly swings back down. This makes parallax error impossible.

The viewing system contains a prism that takes the inverted image from the lens and reverts it for the viewer eye. Thus the viewer sees the scene as it would be normally.

These cameras usually take 35mm film. Some more expensive cameras take larger film sizes. The largest advantage of these cameras is there often ability to have special lens put on them for special viewing, such as telephoto, wide angle, and zoom lens. These cameras come in a wide variety and are the largest supported type of camera in photography.

Twin-Lens Reflex Camera

The predecessor to the SLR camera, this camera almost like a hybrid of the viewfinder and the SLR. The camera has two separate lenses. One is used for viewing and focusing; the other, for taking the picture itself. The image is composed and focused on a ground-glass viewing screen on the top of the camera.

The camera is called a reflex because the light that form the image on the ground glass is reflected off a mirror to turn the image right-side up. Twin-lens reflexes generally use roll film, and often larger than 35mm.

Single-lens Reflex Camera Operations

In the SLR camera the light passes through the lens and is reflected off a mirror cover the film shutter. The light then passes through a Pentaprism where it is reverted. The mirror remains in the same position until the shutter release button is pressed.

When the shutter release button is pressed the viewing mirror rises allowing for the light to pass through to the film plate.

After the shutter closes the mirror returns to its normal position which allows for viewing. When the photographer takes the picture while looking through the viewfinder, he or she will see nothing while looking through the viewfinder for the amount of time set on the shutter speed.