What is Focal Length? - News from Popever.com - Spy Camera Manufacturer China

The focal length of a lens determines the magnification and compression of a scene

Put in simple terms focal length is just a measure of your lens's ability to magnify a scene and is one of the most important attributes of your lens.

Technically, it is defined as the distance in millimetres between the surface of the image sensor and the centre of the lens.

In addition to magnification, it determines the angle of view and compression of the scene. This is quite important to remember so that you know where to stand and what lens to use to get the shot you want.

The longer the focal length (the larger the number in millimetres), the greater the magnification and the closer it will appear that you are to your subjects, but the narrower the angle of view will be.

For this reason long focal length lenses are great for capturing fast action or enlarging objects that are moderately far away. They also require shorter exposure times to minimize burring caused by the shake of hands.

If you adjust your lens to shoot at mid-range between the long and short lengths;

A short focal length on the other hand allows you to see a wider angle view and makes it appear that you are farther away from your subject.