A camera lens which is also known as photographic lens is a series of curved glasses that bring the rays of lights together to form an image. The small optical glass lenses are placed at different lengths from each other.
As a photographer turns the ring located on the barrel of lenses, the pieces of glasses inside the camera moves closer or further away from each other.
A camera lens projects a circular image. However, the sensor captures a relatively small rectangular area at the center of this projected view.
If the rectangle is extended to the edge of this circle, the sensor should be able to capture the full field of view. Conversely, if the rectangle falls short of this, the field of view is then reduced. Most difital cameras use the conventional 35mm format lenses which results to reduced field of view available to the sensor. However, for wider views, a wide-angle converter will be helpful.
Some digital cameras feature zoom lenses with very large ranges where focal length reaches as much as 420mm. And to reduce unsharpness caused by camera shake, an optical image stabilizer is much helpful.
 |
| 55 mm |
 |
| 105 mm |
 |
| 135 mm |
 |
| 200 mm |
These images are taken at the same distance from the object using different focal lengths. Notice how the background gets blurry as the focal length increases? That's because wider lenses tend to magnify distance between objects and
allow greater depth of field. Longer lenses magnify the subject more by
compressing the distance which results to blurry background as the depth of
field gets shallow.
Basic Kinds of Lenses
Normal Lens has focal ranges that are similar to a human eye. 35 to 50mm lenses are considered normal lenses.
Telephoto Lens is the longest and heaviest among the lenses. The subject appears very close but the range of view will be very narrow.
Wide Angle Lens as the name implies has a short but wider views than a typical standard lens of the same focal length. Think of the field of view as captured by a fish where the term fisheye lens is derived. Lenses with focal lengths of 8 to 16mm are considered as fisheye lenses.
 |
| Using Wide Angle Lens |
