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What Is a Camera Lens and How Does It Operate by Kevin Wu

What is a camera lens?

Also known as the photographic objective, objective lens or photographic lens, the camera lens refers to the assembly of lenses that are used at the same time with the camera mechanism and body for the purpose of producing images on the photographic film or any other media that can store image through chemical or electronic processes.

There are no major differences between the camera lens and the video camera, microscope, still camera, the telescope or any other apparatus. What differs is only the construction and design. The lens for camera may be interchangeable or it may be fixed permanently to camera. The interchangeable lenses are of various apertures, focal lengths and other properties and they may be changed depending on the environment and photographic needs of particular event.

How does the camera lens operate?

Most cameras use the rectilinear lenses that are based on the principle of the pinhole. The operation of the pinhole is not very much complicated; it uses tiny aperture that blocks most of the light rays and ends up selecting only one single ray for each image sensor’s point.

The pinhole lenses would be perfect for camera if they did not have the following shortcomings:-

1. The pinhole that has large aperture will produce images that are blurred

2. If the pinhole is made smaller in order to solve problem 1, resolution will be improved but this will cause reduction in the amount of light that is captured

3. The effectiveness of decrease the hole in order to improve image quality is limited by diffraction. At some point, further decreases in the size of the pin hole will lead to darker and blurred images.

The above three shortcomings answer the question of how the pinhole lens can be modified so as to capture more light and produce images in higher resolution. The first step of doing this is by putting simple convex lens that has Focal Length which is equal to the distance of the photographer and the film plane. This simple convex lens is put at the pinhole. This has the effect of opening the pinhole up because the simple convex lens will bend the light that is in proportion to its incidence angle on the camera lens.

The geometry of the modern camera lens is not very different from that of the simple pinhole lens. The difference with the lenses for modern cameras is that the illumination of every image point is provided by focused â€pencil†of rays of light. This is in contradistinction with the simple pinhole lens in which illumination is provided by single light rays.

If you stand at the camera front you can indeed see the small hole and the aperture. The aperture’s virtual image as the camera user sees it from the world is referred to as the entrance pupil of the lens. In this sense, all the light rays that are leaving an object point and that go through the entrance pupil will now be focused to one common point on image film or sensor. This is the basis of design of every camera lens in the world.

Remember

-When the pinhole is very large, the image spot becomes very large and thus the resulting image will be blurred
-When the pinhole is small, the light will be reduced. The diffraction has the effect of preventing the image spot from becoming extremely small.
-When simple lens is used, it is possible to bring in to sharp focus much more light.

The various photographic lenses have more lens elements included. These extra lens elements allow the designers of the lenses to reduce aberrations but the camera lens principle of operation that collection of pencil of rays takes place at entrance pupil from where it the exit pupil focuses it down on the image plain remains the same.

Kevin Wu writes for an Australian online shopping site selling camera lens for digital slr cameras of all the major brands.

Article Source: http://www.earticlesonline.com/Article/What-Is-a-Camera-Lens-and-How-Does-It-Operate/1251286

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