Understanding Focal Length

What is Focal Length

Focal Length measures the amount of magnification of a camera lens. Different lenses have different uses. Sometimes you want to zoom in, or get closer to the subject. Other times you want to take in lots of “real estate”.

Focal lengths are separated into three different categories.

  • Wide-angle focal lengths – wide angle includes lenses that are less than 35mm in focal length. This type of lens is excellent for taking pictures of landscapes and wide panoramas, such as the Grand Canyon and other beautiful vistas. They are also good for taking pictures inside when you can’t back up to get everything into your photo, such as a real estate shot of a bedroom or a large exhibit at the museum. The smaller the number, the wider the area of view in the lens. So, a 12mm lens will be able to get much more of the area than a 24mm lens, even though both are considered “wide-angle” lenses.
    Wide-angle picture

    A wide-angle lens was needed for this barn scene.

  • Normal focal lengths – normal includes lenses from 35mm to 60mm. With a normal focal length, the picture will look similar to what you see as you stand looking at the area you will photograph.
    Normal focal length

    This cemetary bench was taken with a normal focal length of about 50mm.

  • Telephoto focal lengths – Focal lengths of 75mm and above are considered telephoto. They are meant to get a closer view of the subject.
    Telephoto lens

    Telephoto zoom lens was used on this black swallowtail

Multiple Focal Length Lenses (Zoom Lenses)

Zoom lenses have more than one focal length in the same lens. This allows you the flexibility to either magnify the subject by using a larger focal length or shrink your subject by using a smaller focal length. Many zoom lenses include all three categories mentioned above, wide-angle, normal, and telephoto focal lengths.

Single Focal Length Lenses (Prime Lenses)

Prime lenses have only one focal length. The focal length of a prime lens can be wide-angle, normal, or telephoto. Many professionals insist on using only prime lenses for their work, while others use prime and zoom lenses. If you know what you will be shooting beforehand, you can get very good pictures using prime lenses.

Telephoto and Wide-Angle Attributes

Many photographers use telephoto lenses simply to get a closer shot and wide-angle lenses to get more into the picture. However, there are other aspects of focal lengths that you need to know. Camera lenses do not have the same capabilities that the human eye has. They tend to either change the perspective or distort the image at different focal lengths when the camera is moved either toward the subject or away from the subject.

Telephoto lenses are used often for portraits. The telephoto lens does a nice job of isolating the subject and making the background seem to demand less of your visual interest. Because you must back away from the subject when using a telephoto lens, the objects in the background seem to appear bigger, and you capture less of the background, thus making your subject command more attention. On the other hand, if you use a wide-angle lens for a portrait, the background is compressed and looks busier. In addition, you must move closer to the subject when using a wide-angle lens, and parts of the subject tend to be distorted. For instance, the ears may look out of proportion.

Using a wide-angle lens has other considerations, as well. These lenses tend to show more vignetting and barrel distortion, especially when using super wide-angle lenses. If you employ a filter on really sunny days to cut down on the glare, the tendency for vignetting is even stronger. This can be corrected if you are shooting with a zoom lens by zooming in just a bit.