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Lenses

The lens is the camera's most important part.


More than any other camera component, the lens determines the quality of the image.
More than any other camera component, the lens determines the quality of the image.

IMPORTANCE OF THE CAMERA’S LENS

The most important part of a camera is its lens since the quality of an image is so dependent upon it. The most basic camera body fitted with a good lens can make a good picture, but the best camera body in the world cannot make a good picture if its lens is of poor quality - if the image or parts of it are not in focus or if an inadequate amount of light for proper exposure reaches the film or the sensor in a digital camera.


WHAT DOES A LENS DO?

Any lens, even the simplest one, gathers and focuses light.

HOW DOES A LENS WORK?

Light strikes the front surface of the lens and passes through the glass element. Since light rays bend when they enter glass at any angle other than 90, they change direction. The effect is called “refraction.” By employing various glass shapes - forms, really - in their design, lenses are able to channel the light in a specific direction. Focusing occurs because the lens is able to precisely control this direction so that the light rays converge on one point, exactly where the film is located in the camera (or where the CCD is, in the case of a digital camera.)

A lens gathers and focuses light. The quality of your images depends more on the quality of the lens than on any other camera component.
A lens gathers and focuses light. The quality of your images depends more on the quality of the lens than on any other camera component.

Whenever possible, purchase the best lens in its class. This high-quality 80 mm to 200 mm zoom lens is relatively expensive, but the images it produces are exceptional. There is no substitute for quality, especially in lenses.
Whenever possible, purchase the best lens in its class. This high-quality 80 mm to 200 mm zoom lens is relatively expensive, but the images it produces are exceptional. There is no substitute for quality, especially in lenses.

A PHOTOGRAPHIC LENS, TECHNICALLY, IS NOT A “LENS”

A photographic lens is really not a lens at all, although it is called one anyway. A true “lens” is a single piece of glass (or other transparent substance) having one or more curved surfaces used in changing the convergence of light rays. The key word is “single.”

By definition, what we commonly call a photographic lens is more accurately and technically called an “objective.” An objective (or object lens, object glass, objective lens or photographic objective) is an optical system or device containing a combination of lenses that receive light rays from an object and form an image on the focal plane. However, common usage has won in this case. Dictionaries have come to accept the common usage of the term “lens” to mean the entire photographic objective itself, and the archaic term “objective” is rarely seen in use any longer, except in older encyclopedias and dated books on optics. Interestingly, the French word for lens is and remains “objectif.” A photographic lens will always be called a lens, even though it’s not a lens but has a lot of lenses in it. With the exception of the tidbit of information provided in this paragraph, we refer to the photographic objective as a lens throughout the site.

A photographic lens is composed of lenses (ground and polished pieces of formed optical glass) assembled and fitted together in a tube (usually made of metal) called a "lens barrel". The individual lenses are known as “elements” when they are in a photographic lens.


WHAT DOES A GOOD LENS DO?

A good lens allows enough light to pass through it to produce properly-illuminated and sharply defined images on film with short exposure times.

Fortunately, there are few inferior lenses today. If your lens was made in the last twenty-five years or so, odds are it is of good quality since the science and manufacture of lenses has become so advanced. This doesn’t mean that an old lens may not also be of high quality. Many very old lenses were so well made that they remain perfectly serviceable today and continue to render sharp, bright photographs.

It's difficult today to purchase a new lens that wouldn't be considered a good lens for its purposes. Some lenses, however, are not just good, they are incredibly superior in their sharpness and light-gathering abilities.
It's difficult today to purchase a new lens that wouldn't be considered a good lens for its purposes. Some lenses, however, are not just good, they are incredibly superior in their sharpness and light-gathering abilities.

If you will be shooting extreme close-ups that are larger than life, you'll need a good macro lens capable of plenty of depth of field. The particular macro lens shown here also functions as a normal lens, and produces very sharp pictures in general use.
If you will be shooting extreme close-ups that are larger than life, you'll need a good macro lens capable of plenty of depth of field. The particular macro lens shown here also functions as a normal lens, and produces very sharp pictures in general use.

There are varying degrees of “good” lenses - sort of a good, better, best range. Sharp lenses that are very fast, for example, generally cost much more.

When we say a lens is fast, it’s a reference to its largest aperture, or widest possible opening. A fast lens has a very wide maximum opening, allowing more light to pass through the lens, therefore permitting the photographer to use faster shutter speeds or to shoot in dimmer light.

Generally, the larger a lens’s maximum aperture, the more expensive the lens is.

If you are using a digital camera, you are advised to select the best quality lenses for it that you can afford, since image sensors respond to light in a different manner than does film. The grain in film is of differing sizes, but pixels are all the same size. Light directly striking an image sensor is recorded slightly differently than light striking it an angle, which causes a small loss of sharpness which can be especially noticeable at the edges of a digital image when using a wide-angle lens. A quality lens can help to reduce this lack of sharpness.


MORE ON LENSES

This section of photographytips.com in conjunction with our section entitled Aperture should provide you with a good deal of information about lenses. If, however, you have a tip, pointer or general information about lenses that we missed and that could be important to our viewers, please send it to us. If we use it, we’ll credit you with the information, and you may become famous. If your submission would benefit by an image to better clarify your information or to illustrate your tip, please send one along. If you took the picture, we’ll credit you as the photographer, and you’ll be doubly famous.

When the same lens is focused for extreme macro close-ups of tiny subjects, however, its quality really comes out. You will never regret buying the best lenses you can afford within your budget.
When the same lens is focused for extreme macro close-ups of tiny subjects, however, its quality really comes out. You will never regret buying the best lenses you can afford within your budget.
Further information...

Lens types

Lens speed

Depth of focus
Related topics...

Refraction

Aperture

Optimum aperture

Lenses for aerial photography

Lenses that attach like filters

Lens choice for family groups

Lens choice for portraiture

Using 35mm SLR lenses on dSLR camera bodies

That annoying lens cap

Lens distortion