Relationship Between Focal Length & Magnification


Learning about focal length and magnification is a fundamental step to becoming a good photographer. They determine what lens you will choose for your subject and how your subject will appear when photographed. Further, they will also affect other aspects of your camera such as shutter speed and aperture settings.

What Is Focal Length?

  • Focal length is the distance from the lens to the focal plane (the surface on the inside of your camera where your lens forms a sharp image) when the camera is set to take a photograph at its farthest distance.


  • Focal length controls the magnification within your camera lens. The longer the camera lens the greater the magnification. The shorter the camera lens the smaller the magnification. This is because of the way the lens bends light when light passes through it. A small lens is forced to bend light rays sharply, which results in a smaller image. In contrast, a longer lens does not bend the light so abruptly, allowing for larger image to recorded.

Angle of View

  • Focal length also controls the angle of view: the cone of vision that you see from your camera's viewfinder. As you gradually begin to extend your lens or "zoom in" on your subject your cone of vision begins to shrink. A good analogy of this would be the older square television sets versus the new wide-screen televisions. Short focal lengths allow you to see more of the scene in the manner of how a wide-screen television does; however, longer focal length lenses allow you to see a magnified picture, but with a smaller range of sight like the screen of an older television set.

The Short Lens

  • The longer your camera lens is doesn't mean the better your picture is going to be. It all depends upon the subject matter and the lighting of your subject. Short lenses have short focal lengths that allow them the advantage of shooting a subject at a wide angle and to create a more natural feel to the image. Short lenses or normal focal length lenses see most closely to what the human eye sees naturally. They are also able to take faster photos because they absorb more light than a longer lens. The biggest drawback to these lenses, however, is that they force you to get close to your subject.

The Long Lens

  • Longer lenses, or telephoto lenses as they're more commonly called, will allow you to take the shot from a distance. Other advantages including greater perspective between close and far object and less distortion at close range.

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  • Photography; Barbara London, John Upton, Kenneth Kobre and Betsy Brill; 2002
  • Photo Credit Image by, courtesy of Shazeen Samad
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