Magnification is the process of enlarging something only in appearance, not physical size. Magnification is also a number describing by which factor an object was magnified. In some fields, this number may be less than one, corresponding to an apparent reduction in size. This is sometimes called minification.

Typically magnification is related to scaling up visuals or images to be able to see more detail, increasing resolution, using optics, printing techniques, or digital processing. In all cases, the magnification of the image does not change the perspective of the image. Vision can refer to: Visual perception is one of the senses. ... Image of the Wikimedia Commons logo. ... Angular resolution describes the resolving power of a telescope. ... Table of Opticks, 1728 Cyclopaedia Optics (appearance or look in ancient Greek) is a branch of physics that describes the behavior and properties of light and the interaction of light with matter. ... The folder of newspaper web offset printing press Printing is a process for production of texts and images, typically with ink on paper using a printing press. ... Digital processing is the process of altering digital data in any form, for any purpose. ... Perspective when used in the context of vision and visual perception refers to the way in which objects appear to the eye based on their spatial attributes or dimension and the position of the eye relative to the objects. ...

Magnification as a number (optical magnification)

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. In dimensional analysis, a dimensionless number (or more precisely, a number with the dimensions of 1) is a pure number without any physical units. ...

• Linear magnification — For real images, e.g., images projected on a screen, size means a linear dimension (measured, e.g., in millimeters or inches).

• Angular magnification — For optical instruments with an eyepiece, the linear dimension of the image seen in the eyepiece (virtual image in infinite distance) cannot be given, thus size means the angle subtended by the object at the focal point (angular size). Strictly speaking, one should take the tangent of that angle (in practice, this makes a difference only if the angle is larger than a few degrees). Thus, angular magnification is defined as

,

where is the angle subtended by the object at the front focal point of the objective and is the angle subtended by the image at the rear focal point of the eyepiece.

• Example: The angular size of the full moon is 0.5°, in binoculars with 10x magnification it appears to subtend an angle of 5°, which is roughly 1/10th of the field of view of typical eyepieces.

By convention, for magnifying glasses and optical microscopes, where the size of the object is a linear dimension and the apparent size is an angle, the magnification is the ratio between the apparent (angular) size as seen in the eyepiece and the angular size of the object when placed at the conventional closest distance of distinct vision of 25 cm from the eye.

Optical magnification is sometimes referred to as "power" ("10x power", "high-power eyepiece"). Real image is a term used in optics and physics. ... Mid-19th century tool for converting between different standards of the inch An inch is an Imperial and U.S. customary unit of length. ... ... An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. ... Top: The formation of a virtual image using a concave lens. ... Angular size is a measurement of how large or small something is using rotational measurement (degrees of arc, arc_minutes, and arc-seconds). ... Wikibooks has more about this subject: Trigonometry Table of Trigonometry, 1728 Cyclopaedia Trigonometry (from the Greek trigonon = three angles and metro = measure) is a branch of mathematics dealing with angles, triangles and trigonometric functions such as sine, cosine and tangent. ... Angular size is a measurement of how large or small something is using rotational measurement (degrees of arc, arc_minutes, and arc-seconds). ... Binoculars Binocular telescopes, or binoculars, are two identical or mirror-symmetrical telescopes mounted side-by-side and aligned to point accurately in the same direction, one to be viewed through each of the users eyes. ... An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. ... A magnifying glass A magnifying glass is a single convex lens which is used to produce a magnified image of an object. ... It has been suggested that microscopy be merged into this article or section. ...

Calculating the magnification of optical systems

• Single lens: The linear magnification is

M = f / (f − S)

where f is the focal length and S is the distance from the lens to the object. Note that for real images, M is negative and the image is inverted. For virtual images, M is positive and the image is upright.

• Telescope: The linear magnification is given by

M = f_e / f_o

where f_o is the focal length of the objective lens and f_e is the focal length of the eyepiece. The angular magnification is given by

MA = f_o / f_e

• Magnifying glass: The angular magnification is given by

MA = 25cm / f + 1 for normal cases, and

MA = 25cm / f for image at infinity,

where f is the focal length of the lens in centimeters.

• Microscope: The angular magnification is given by

where M_o is the magnification of the objective and M_e the magnification of the eyepiece. The magnification of the objective depends on its focal length f_o and on the distance d between objective back focal plane and the focal plane of the eyepiece (called the tube length):

M_o = d / f_o.

The magnification of the eyepiece depends upon its focal length f_e and can be calculated by the same equation as that of a magnifying glass (above).

Note that both astronomical telescopes as well as simple microscopes produce an inverted image, thus the equation for the magnification of a telescope or microscope is often given with a minus sign. A lens. ... Real image is a term used in optics and physics. ... Top: The formation of a virtual image using a concave lens. ... 50 cm refracting telescope at Nice Observatory. ... The focal point F and focal length f of a positive lens, a negative lens, a concave mirror, and a convex mirror. ... An objective lens is the lens in a microscope, telescope, camera or other optical instrument, that receives the first light rays from the object being observed. ... The focal point F and focal length f of a positive lens, a negative lens, a concave mirror, and a convex mirror. ... An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. ... A magnifying glass A magnifying glass is a single convex lens which is used to produce a magnified image of an object. ... The focal point F and focal length f of a positive lens, a negative lens, a concave mirror, and a convex mirror. ... A lens. ... It has been suggested that microscopy be merged into this article or section. ... The focal point F and focal length f of a positive lens, a negative lens, a concave mirror, and a convex mirror. ... The focal plane of a lens is a plane that is perpendicular to the axis of the lens and passes through its focus. ... An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. ... An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. ... The focal point F and focal length f of a positive lens, a negative lens, a concave mirror, and a convex mirror. ... A magnifying glass A magnifying glass is a single convex lens which is used to produce a magnified image of an object. ... The plus and minus signs (+ and −) are used universally to represent the notions of positive and negative as well as the operations of addition and subtraction. ...

Measurement of telescope magnification

Measuring the actual angular magnification of a telescope is difficult, but it is possible to use the reciprocal relationship between the linear magnification and the angular magnification, since the linear magnification is constant for all objects.

The telescope is focussed correctly for viewing objects at the distance for which the angular magnification is to be determined and then the object glass is used as an object the image of which is known as the Ramsden disc. The diameter of this may be measured using an instrument known as a Ramsden dynamometer which consists of a Ramsden eyepiece with micrometer cross hairs in the back focal plane. This is mounted in front of the telescope eyepiece and used to measure the diameter of the Ramsden disc. This will be much smaller than the object glass diameter, which gives the linear magnification (actually a reduction), the angular magnification can be determined from

MA = 1 / M = D_Objective / D_Ramsden

Other uses

• One can also magnify sounds (see amplification).
• Magnification can also be used as a generalized term for increasing the detail or vividness of something: ideas, emotions, etc.
• A Magnification factor is sometimes poorly used to desribe the scale of an image such as a microscopic image published on the web. Since the eventual size of the display cannot be controlled, a notation such as 50x is meaningless. A better practice is to include a scale bar or other object of known size in the image. In certain art-pictures, such as Nikon Small World Gallery, scale bars are undesirable for aeshthetic reasons. In such cases, it would be better to include a caption stating the size of some apparent feature or state the field size of the original image.

An amplifier can be considered to be any device that uses a small amount of energy to control a source of a larger amount of energy, although the term today usually refers to an electronic amplifier. ... An idea (Greek: ιδέα) is the result of thinking. ... Emotion, in its most general definition, is a neural impulse that moves an organism to action, prompting automatic reactive behavior that has been adapted through evolution as a survival mechanism to meet a survival need. ...

See also

• Magnifying glass
• Microscope
• Optical telescope
• Lens