In
photography
Photography is the visual arts, art, application, and practice of creating images by recording light, either electronically by means of an image sensor, or chemically by means of a light-sensitive material such as photographic film. It is empl ...
, exposure range may refer to any of several types of
dynamic range
Dynamics (from Greek δυναμικός ''dynamikos'' "powerful", from δύναμις ''dynamis'' " power") or dynamic may refer to:
Physics and engineering
* Dynamics (mechanics), the study of forces and their effect on motion
Brands and ent ...
:
* The ''
light sensitivity range'' of photographic film, paper, or digital camera sensors.
* The ''luminosity range'' of a scene being photographed.
* The ''opacity range'' of developed film images
* The ''reflectance range'' of images on photographic papers.
The exposure range of a device is usually expressed in stops, which are equivalent to
where ''c'' is the medium or device's
contrast ratio
The contrast ratio (CR) is a property of a display system, defined as the ratio of the luminance of the brightest shade (white) to that of the darkest shade (black) that the system is capable of producing. A high contrast ratio is a desired aspec ...
. For example, average
Digital Video (DV) has a contrast ratio of 45:1, so its exposure range is roughly 5.5 stops.
Film
A film, also known as a movie or motion picture, is a work of visual art that simulates experiences and otherwise communicates ideas, stories, perceptions, emotions, or atmosphere through the use of moving images that are generally, sinc ...
has an exposure range of approximately 14 stops.
Exposure is usually controlled by changing the lens aperture (the amount of light it gathers), the shutter speed (how long light is gathered) or sensitivity (how strongly the film or sensor responds to light). Changing exposure does not change the exposure range.
A
graduated neutral density filter
A graduated neutral-density filter, also known as a graduated ND filter, split neutral-density filter, or just a graduated filter, is an optical filter that has a variable light transmission. Typically half of the filter is of neutral density wh ...
can be also used to improve the reproduction of the exposure range of the scene, by darkening bright parts of the image.
A graduated filter will reduce the extreme highlights of an image, such as a clear, open sky as well as sunlight. The filter is usually an even gradation of neutral gray to clear, covering the top third to half of the filter in gray. Therefore, it mostly affects the top third to half of the frame's exposure, leaving the highlights in the bottom half to two-thirds unaffected. Often these filters are the square gelatin,
polycarbonate
Polycarbonates (PC) are a group of thermoplastic polymers containing carbonate ester, carbonate groups in their chemical structures. Polycarbonates used in engineering are strong, toughness, tough materials, and some grades are optically transp ...
, or glass type. A mounting kit such as a square frame receptacle mounted to interchangeable screw-in rings will hold the filter at an appropriate orientation. These can be mounted to the end of an SLR lens camera in the same fashion as a polarizing lens, UV filter, and various other screw-in type filters for SLR and DSLR cameras.
See also
*
Exposure latitude
Exposure latitude is the extent to which a light-sensitive material can be exposed (overexposed or underexposed) and still achieve an acceptable result. It is relevant to both digital and analogue processes such as photolithography and photography ...
*
High dynamic range imaging
High dynamic range (HDR), also known as wide dynamic range, extended dynamic range, or expanded dynamic range, is a signal with a higher dynamic range than usual.
The term is often used in discussing the dynamic ranges of images, videos, audio or ...
References
Science of photography
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