Nikon camera lenses often have a extensive series of letters before and after the focal length, such as AF-S 70-300mm 1:4.5-5.6 G. To the unknowing, all those letters can look like alphabet soup. Knowing how to decipher the letters can instantly tell a user the features of the lens, as well as the cameras on which the lens will work.
Nikon introduced the f-mount lens mounting system in 1959, and there have not been any notable changes. That is good news for consumers, because film camera lenses manufactured decades ago with what Nikon calls automatic indexing, or AI, can be used on the company's new digital cameras. While the mounting system has not significantly changed, Nikon has introduced several new lens features.
Nikon manufactured its first autofocus lens in 1986. The acronym is AF. AF-D lenses told the camera the focusing distance. This is beneficial when using a flash and taking a picture of a subject that takes up only a small portion of the frame. The distance information helps the camera get the correct exposure. AF-S lenses are the only lenses that will focus on the D40 model. DX lenses are made for cameras that do not have full-frame sensors.
If you are using the most recent Nikon cameras, a D-type or a G-type lens will provide the most metering and flash capability. If you use any other lens type, you will be giving up something in automatic metering or through-the-lens flash metering. The D40, D40x, D60 and D5000 camera body models will only autofocus with an AF-S lens. An AF-S lens has a silent wave integrated focus motor in it.
VR means vibration reduction. Nikon introduced this feature in 2000. It helps take out blur when a camera cannot be held still. It is useful for taking handheld pictures in low-light situations. It eliminates the need to use a tripod in some conditions.
Lenses manufactured between 1959 and 1977 are called pre-AI lenses. Do not mount these lenses on any of the newer Nikon cameras except the D40, D40x, D60, D5000, a modified F5, a modified F6 or an F4. Mounting on any other camera can cause damage to the camera mount. A pre-AI lens has a solid coupling prong. Compatibility charts are available online.
Lens have two sets of numbers. The number followed by "mm" is the focal length. The larger the focal length, the more the subject is magnified. The second number is the minimum f-stop for that lens. The f-stop, also called aperture, determines how much light the lens allows in and the photo's depth of field. A lower f-stop means a narrow depth of field, and more light is allowed into the lens. A zoom lens can have different minimum f-stops for different focal lengths.