what does the f/1.8 II on camera lens? the speed? help! thanks =D Well, for a lens, I guess we do call this the "speed," as in, "An f/1.8 lens is a fast lens."
It is actually the maximum opening (aperture) of the lens. If the opening is large, which f/1.8 is, the lens is said to be a fast lens, because you don't have to leave the shutter open very long for an adequate exposure. For instance, if the proper exposure is 1/60 at f/4, it would be about the same at 1/250 at f/1.8, so you can use a faster shutter speed at the larger (f/1.8) opening. This is why f/1.8 is said to be faster than f/4, even though the f-stop is actually a static measurement of the ratio of the diameter of the aperture to the focal length of the lens. YW Report It
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