Magnification

Magnification is the process of enlarging the apparent size, not physical size, of something. This enlargement is quantified by a size ratio called optical magnification. When this number is less than one, it refers to a reduction in size, sometimes called de-magnification. Typically, magnification is related to scaling up visuals or s to be able to see more detail, increasing resolution, using microscope, printing techniques, or digital processing. In all cases, the magnification of the image does not change the perspective of the image. Some optical instruments provide visual aid by magnifying small or distant subjects. A magnifying glass, which uses a positive (convex) lens to make things look bigger by allowing the user to hold them closer to their eye. A telescope, which uses its large objective lens or primary mirror to create an image of a distant object and then allows the user to examine the image closely with a smaller eyepiece lens, thus making the object look larger. A microscope, which makes a small object appear as a much larger image at a comfortable distance for viewing. A microscope is similar in layout to a telescope except that the object being viewed is close to the objective, which is usually much smaller than the eyepiece. A slide projector, which projects a large image of a small slide on a screen. A photographic enlarger is similar. A zoom lens, a system of camera lens elements for which the focal length and angle of view can be varied. Optical magnification is the ratio between the apparent size of an object (or its size in an image) and its true size, and thus it is a dimensionless number. Optical magnification is sometimes referred to as "power" (for example "10× power"), although this can lead to confusion with optical power. For s, such as images projected on a screen, size means a linear dimension (measured, for example, in millimeters or inches). For optical instruments with an eyepiece, the linear dimension of the image seen in the eyepiece ( at infinite distance) cannot be given, thus size means the angle subtended by the object at the focal point (angular size).