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

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2016-01-09 19:42:24

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.


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