What Do All Of Those Numbers On My Lens Mean?

by Holly on June 26, 2012

in Tech

You finally got that DSLR camera you have been pining over for so long. Good-bye point-and-shoot and hello shutter speeds, f-stops, and manual settings. Taking complete control over your camera requires understanding what the different functions and numbers mean. One thing you may notice is that there are quite a few numbers on the lens alone.

So what do the numbers on the lens mean?

Focal Length

The number(s) on the lens that are depicted in mm represent the focal length of the lens. The focal length is the distance the front of the lens sits from the sensor at the back of the lens. The smaller number takes a wider view of the scene in front of you—18 mm for example. The larger number creates a magnified view of the scene—200 mm for example.  If there is only one number—like 50 mm—the lens has a fixed focal length and is considered a prime lens. If there are two numbers on the lens—such as 18–55 mm or 80–210 mm—the lens is considered a zoom lens.

Widest Aperture for the Lens

The numbers represented by a ratio indicate the widest aperture available for the lens. An aperture range of 1:3.5–5.6 means that the lens can stop down to 3.5 at the widest end of the lens’ focal length—18 mm in this example and f/5.6 at the longest end of the lens’ focal length—55 mm for the lens in the photo above. But what does aperture mean? The aperture determines how much light is allowed into the camera when the shutter is clicked. A low aperture number like f/5.6 will allow a lot of light in but will result in a shallow depth of field. A higher aperture number like f/16 will allow only a small amount of light in but will result in a larger depth of field which is the range at which things are in focus in a photograph.

Ring Diameter

A number following by a Greek symbol Phi—Φ58 mm—represents the diameter of lens filters that will fit that particular lens. If you happen to have a filter that does not fit your lens, you can buy converter rings that will compensate for the discrepancy.

These numbers will help you when you are trying to decide which lenses and filter to add to your collection. If you tend to shoot portraits you may want to go with a 50 mm lens. If nature photography is more your style and you want to be able to photograph your subjects from a distance without disturbing them, pick up a telephoto zoom lens with a higher focal length.

Whatever you choose, just get out there and shoot.

Holly teaches design at a small NW Ohio college. She spends her days off hanging out with her foxy musician husband and their gorgeous new baby and ridiculously smart pre-school aged son. Holly has a passion for food, photography, beautiful letter forms, and the possibilities that can be found in a single sheet of well made paper. You can read more from Holly on her blog, Artist Mother Teacher.

photo credit

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