All types of lenses are available in the market has a point where if we move closer to the object image, the lens will not focus (blur). In general, this point is called the Minimum Focusing Distance (MFD) or a minimum focusing distance. MFD is expressed in units of length (eg 0.5 m) measured from the distance of the light sensor in the camera until the object image. If a lens, like the photo above has the MFD 0.25 meter (25 cm) means that the minimum distance of the object image to the image sensor so that images remain sharp is 25 centimeters, so we take photos of objects closer to the camera, the image will begin to blur.
Minimum Focusing Distance scale information is usually written on the lens itself (like the photo above), if you are confused look at the lens, you will still find it in the technical specifications in the manuals or catalogs lens.
Information on the MFD is actually not much use for the general user, but if you are fond of macro photography (close up), how the MFD of a lens is important information. Because of the initial macro lens is designed to meet the needs of macro photographers, then to the average macro lens, its MFD can reach 16 cm. And because the distance of 16 cm was measured from the position of the light sensor - the object image, then we can put the proverbial tip of the lens to the object image and the macro lens is still able to take focus.
While the MFD for the category of SLR lenses (non macro) is usually about 30 cm or more. For example, Nikon 50mm f/1.4 G lens is written below have MFD 0.45 m (equal to 45 cm MFD).
