What is the meaning of 18-135mm f3.5-5.6g ed-if af-s dx?

Answer 1

This is a Nikon lens that was originally released around 2005. AF-S stands for Auto Focus-Silent Wave Motor. This means that the lens has an autofocus motor built into it, so the cameras used with it do not have to have AF motors built into them. "DX" refers to the size of the camera sensor; the sensor has a 1.5x crop, which affects the focal length and the aperture. "18-135mm" refers to the range of focal lengths of the lens. "f/3.5-5.6" refers to the aperture of the lens; as the lens is zoomed in to longer focal lengths, the aperture gradually increases from f/3.5 to f/5.6. "ED" refers to the Extra-Low Dispersion elements, which reduce the chromatic aberration of the lens. IF stands for Internal Focus, which means the lens length does not change when focusing. The front element of this lens does not rotate when focusing either, so the orientation of front mounted accessories such as polarizing filters does not change during focusing.

In Photography, the "focal length" of a lens is usually stated in millimeters (mm). The higher the number, the greater the magnification. A "normal" focal length for a 35mm film camera is around 50mm. A focal length of 18mm is considered "wide angle" and 135mm is sometimes referred to as a "portrait" lens. Lenses with higher numbers (200-1000) may be called "tele-photo". The listing for a lens as 18-135mm means it is a "zoom" lens. This means the focal length can be changed by the photographer usually by turning a ring on the body of the lens. As to "f3.5-5.6", in this listing, it is the range of the maximum size of the aperture. The aperture is the opening in the camera that allows light in to take the picture. The f number -- called the "f-stop" is calculated by dividing the diameter of the aperture opening by the focal length of the lens and expressing the answer as a properly reduced fraction (with the top number a 1). The f-stop is the bottom of the fraction. For example: a camera with a 100mm lens that has a maximum aperture of 50mm, or an "f-stop" of 2 (50/100=1/2). On a zoom lens, since the focal length changes, but the aperture does not, the f-stop will change with the focal length. So, the first number 3.5 means at the lower focal length (18mm) the maximum aperture opening is 1/3.5th of the focal length, or about 5mm. The other number 5.6 means at the higher focal length (135mm) the maximum aperture opening is 1/5.6th of the focal length, or about 24mm.