Focal Length: How far your camera can see

Technically, the focal length is the distance from a camera lens to a film or a sensor (the digital version of film). This value determines how wide the camera is able to see. The less focal length gives the wider angle. On the other hands, the higher focal length means cameras could see farther.

For example, suppose a focal length of your camera can be adjusted from 35mm to 105mm (3x zoom). The widest and the narrowest view it can see is about 62 and 23 degree of arc respectively. Note that the 23 degree view also provides the most zoom at the same time.

The focal length is one important ingredient of selecting the perfect fit digital camera. Basically, your shooting style and preferences can tell what length is the best for you. If you like to take landscape pictures, you might wanna stick with low focal length because, with the wide angle lens, you can capture wider images. In contrast, if you tend to take wildlife behaviors or you are a bird watcher, you definitely need the telephoto lens or the lens with high focal length.


The figure below shows the relationship between the focal length and the degree of arc that cameras could see.

The next four images are captured with four different focal lengths. (source: wikipedia)

	28mm
	50mm
	70mm
	210mm

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