Focal Length

"It's all about perspective!"

The focal length of a camera lens assembly is the distance between the front lens of a camera and the point that focuses on the film or image sensor. With a zoom lens, which most lenses are nowadays, this is measured at the lens’s maximum focal distance (when the front lens is furthest from the camera).

Common Lengths

These lengths are commonly measured in millimeters.

Different kinds of lenses have different ranges of lengths.

• Wide angle zoom lenses : 15 – 35mm
• Standard zoom lenses : 24 - 70mm
• Telephoto zoom lenses : 70 - 500mm

Angle of View

The actual reason that subjects look closer as these lengths increase is the change in the angle of view. This is the angle offset from a line perpendicular to the center of the front lens face where borders of the camera’s field of view end. Common Angles of View

• Wide angle lenses: 100° - 60°
• Normal lenses: 50° - 25°
• Telephoto lenses: 15° - 8°

In the long run, as the focal length of the lens increases, the angle of view decreases allowing the lens to project a smaller area onto the full size of the film or image sensor. This is what allows us to use different lenses to take pictures of objects at different distances and make them appear closer.

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