The aspect ratio of a geometry shape is the ratio of its sizes in different dimensions. For example, the aspect ratio of a rectangle is the ratio of its longer side to its shorter side—the ratio of width to height,
The aspect ratio is most often expressed as two integer numbers separated by a colon (x:y), less commonly as a simple or decimal fraction. The values x and y do not represent actual widths and heights but, rather, the proportion between width and height. As an example, 8:5, 16:10, 1.6:1, and 1.6 are all ways of representing the same aspect ratio.
In objects of more than two dimensions, such as , the aspect ratio can still be defined as the ratio of the longest side to the shortest side.
Applications and uses
The term is most commonly used with reference to:
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Graphic / image
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Image aspect ratio
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Display aspect ratio
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Paper size
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Standard photographic print sizes
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Motion picture film formats
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Standard ad size
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Pixel aspect ratio
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Photolithography: the aspect ratio of an etched, or deposited structure is the ratio of the height of its vertical side wall to its width.
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HARMST High Aspect Ratios allow the construction of tall microstructures without slant
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Tire code
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Tire sizing
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Turbocharger impeller sizing
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Wing aspect ratio of an aircraft or bird
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Astigmatism of an optical lens
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Nanorod dimensions
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Shape factor (image analysis and microscopy)
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Finite Element Analysis
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Flag design; see List of aspect ratios of national flags
Aspect ratios of simple shapes
Rectangles
For a rectangle, the aspect ratio denotes the ratio of the width to the height of the rectangle. A
square has the smallest possible aspect ratio of 1:1.
Examples:
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4:3 = 1.: Some (not all) 20th century computer monitors (VGA, XGA, etc.), standard-definition television
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: international paper sizes (ISO 216)
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3:2 = 1.5: 35mm still camera film, iPhone (until iPhone 5) displays
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= 1.6: commonly used widescreen (WXGA)
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Φ:1 = 1.618...: golden ratio, close to 16:10
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5:3 = 1.: super 16 mm, a standard film gauge in many European countries
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16:9 = 1.: widescreen TV and most laptops
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2:1 = 2: dominoes
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64:27 = 2.: ultra-widescreen,
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32:9 = 3.: super ultra-widescreen
Ellipses
For an
ellipse, the aspect ratio denotes the ratio of the
major axis to the
minor axis. An ellipse with an aspect ratio of 1:1 is a
circle.
Aspect ratios of general shapes
In
geometry, there are several alternative definitions to aspect ratios of general
in a d-dimensional space:
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The diameter-width aspect ratio (DWAR) of a compact set is the ratio of its diameter to its width. A circle has the minimal DWAR which is 1. A square has a DWAR of .
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The cube-volume aspect ratio (CVAR) of a compact set is the d-th root of the ratio of the d-volume of the smallest enclosing axes-parallel d-cube, to the set's own d-volume. A square has the minimal CVAR which is 1. A circle has a CVAR of . An axis-parallel rectangle of width W and height H, where W> H, has a CVAR of .
If the dimension d is fixed, then all reasonable definitions of aspect ratio are equivalent to within constant factors.
Notations
Aspect ratios are mathematically expressed as
x:
y (pronounced "x-to-y").
Cinematographic aspect ratios are usually denoted as a (rounded) decimal multiple of width vs unit height, while photographic and videographic aspect ratios are usually defined and denoted by whole number ratios of width to height. In there is a subtle distinction between the display aspect ratio (the image as displayed) and the storage aspect ratio (the ratio of pixel dimensions); see Distinctions.
See also
