Photography Equipment - Camera Lenses

Camera Lens Basics

The photographic lens, which is also known as an objective lens (photographic objective), is an optical lens or assembly of lenses which are used in conjunction with the camera body and mechanism in order to make images of objects.  This can then be either placed on to photographic film, or any other media, which is capable of storing an image either chemically or electronically.

Such a lens will often incorporate an aperture adjustment mechanism.  This will often be an iris diaphragm which regulates the amount of light that may pass through.  It will have a shutter in order to regulate the time during which the light may pass through, and this can either be incorporated within the lens assembly, or it may be within the camera itself.  In some cases (although very rare), it will be in front of the lens.

The way to focus a lens is by adjusting the distance from the lens assembly to the image forming surface by moving elements that are contained within the lens assembly.

A lens is made up of the following elements.

1. Transparent Material.  This is often glass, as it has good optical properties and is resistant to scratching.  However, various plastics, such as acrylic or Plexiglas, may be used instead.

2. Aperture and Focal Length.  The maximum usable aperture is usually specified as the focal ratio (f-number) on a lens.  This is equal to the focal length which is divided by the effective aperture (entrance pupil) diameter in the same units.  So the lower the number, the more light per unit area will be delivered to the focal plane.

3. Many practical lens assemblies will also contain mechanisms which deal with measuring light and will hold the aperture open until the instant of exposure to allow the camera to focus with a bright image.

What types of lenses are there?

Basic Lens Types

There are three basic types of lenses:-

1. Wide

2. Normal

3. Telephoto

All these lenses, in some way, warp what a person is looking at.  So the way in which they focus light can make the foreground and background appear really close together or at a distance from each other.

But a normal lens is one where these layers of an image will appear almost the same as what the human eye is seeing.

A wide lens will push the background away from the user, and telephoto does the opposite and brings the background in closer.

However the most popular kinds of camera lenses are known as zoom lenses.  These are extendable lenses which are usually (but not always) including wide, normal and telephoto, which is built into the one lens.

However, over the years, a lot of photographers have been faced with the lenses they are using being quite big and heavy, making them hard to hold.  So any slight shake while using one of these types of lenses can end up with a photographer having a blurred image.  However there are many modern large lenses which have a stabilization mechanism which actually counteracts the photographer's movements, and so nearly eliminates all signs of shakiness in their photographs.

Also, you will find that lenses have different coatings on them.  There are some which help to fight reflection in an image, while others account for things such as UV blocking.

However, when deciding where to start when purchasing a lens for your camera it is best to begin with a normal lens, then move on to an ultra wide, as it will give you the clearest indication of what a lens actually does.