How Digital Cameras Work: Lenses

One of the primary aspects of a digital camera is the lens. It is the part of the camera that controls virtually everything about how the image will look. There are several types of lenses, Standard, Tele-photo, Wide-angle, etc. but all of these lenses follow the same general principals and function in the same general way. The only real difference between lenses is how they manipulate light and how the internal lenses are set up.

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Parts of a Lens
When most people think of lenses they tend to think of the strange looking pieces of glass, that were either fat or inverted. These pieces of glass are the exact same thing that makes up a cameras lens. The two most basic types of lenses are a convex (the fat one) and concave (the inverted one) lens. These lenses manipulate light as it is passed through them. A typical camera lens contains anywhere between 5-7 of these lenses, all of which manipulate the light as it passes through. These lenses are usually specially designed, depending on the type of camera lens you are using, to bend light to suit the needs of the photographer. This can mean creating an extreme zooming effect or maintaining a strong depth of field. Typically the only constant light manipulation between lens types is manipulating light to pass through the center of the aperture.

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The second part of a lens is the aperture component. This is one of the most crucial elements in the lens for controlling photography. This component is what allows specific levels of light through the lens. It is often made up of a series of 5-9 interwoven blades that are controlled by a motor to ensure correct f-stops. The degree to which the aperture is open is commonly referred to as f-stops and are usually displayed in f-numbers (such as f/8, f/11, or f/16). I will explain more about the aperture later on.

Image by Takashi(aes256)

One of the key elements of a lens that often goes unmentioned but serves one of the greats jobs in this component is the housing of the lens. The lens’s housing not only holds all of the other elements in place, but also ensures that no additional light is let in. For most lenses the housing of the lens also features three elements that many people also over look the importance of. The first of these is the locking mechanism that locks your lens into the camera body. The two other elements on the lens housing is that of the zoom control and the focus control. Each of these controls manipulate the internal lenses, which in turn manipulate the incoming light. The manipulation of these elements will either zoom in or zoom out on a subject or create a sharper image. The focus control is often times left to the camera in the instance of auto focus, but can still be controlled manually by turning auto focus off.

A new addition to many lenses is a special component label “VR”. This component is a lenses “vibration reduction” component that is designed to prevent blur from minor shaking of the camera.