Friday, 17 October 2014

Angle of View of Camera Lenses

Angle of view of a lens is what the lens sees or simply what you are able to see when looking through the viewfinder. Angle of view changes according to the focal length of the lens mounted on the camera. The longer the focal length of the lens; the narrower the angle of view and shorter the focal length wider the angle of view.

Focal Length and Angle of View of Camera Lens
Focal Length and Angle of View of Camera Lens

Lenses with long focal lengths are called tele photo lens and that of short focal length are called wide angle lenses. When shooting a subject from the same distance, a wide angle lens which has a wide angle of view will capture a large area making the subject relatively smaller in the picture and a tele photo lens which has a narrow angle of view will capture only a small portion of the scene making the subject seem much larger.

Angle of view can be measured vertically, horizontally or diagonally and it changes with sensor size. Back in the ‘film days’ what the lens used to see (angle of view) was said to be the focal length of the lens.

I.e. angle of view = focal length; for 35mm film or full frame digital cameras.

But with cameras that use a sensor smaller than full frame, the focal length of the lens need to be multiplied with the crop factor to get the angle of view of the lens.

For example a 100mm lens mounted on a crop sensor camera with a crop factor of 1.6 x.

Angle of view = focal length 100 * crop factor 1.6 = 160

So for cameras using a crop sensor the angle of view could only be calculated; if sensor dimensions are known.

In case of zoom lenses where the angle of view changes with zoom. For example an 18 – 55mm zoom lens has the widest angle of view at 18mm and narrowest angle of view at 55mm and also covers everything in between.

Classification of Lenses according to Angle of View

Based on their angle of view lenses could be broadly classified into three categories. Normal Lens, Wide angle Lens and Tele Photo Lens. In the next article we will discuss normal lenses in detail.