Exposure range
Encyclopedia
In photography
, exposure range may refer to any of several types of dynamic range
:
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
. For example, average Digital Video (DV)
has a contrast ratio of 45:1, so its exposure range is roughly 5.5 stops. Film
has an exposure range of approximately 14 stops, currently the highest in motion picture mediums.
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
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
, 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.
Photography
Photography is the art, science and practice of creating durable images by recording light or other electromagnetic radiation, either electronically by means of an image sensor or chemically by means of a light-sensitive material such as photographic film...
, exposure range may refer to any of several types of dynamic range
Dynamic range
Dynamic range, abbreviated DR or DNR, is the ratio between the largest and smallest possible values of a changeable quantity, such as in sound and light. It is measured as a ratio, or as a base-10 or base-2 logarithmic value.-Dynamic range and human perception:The human senses of sight and...
:
- The Light sensitivity rangeFilm speedFilm speed is the measure of a photographic film's sensitivity to light, determined by sensitometry and measured on various numerical scales, the most recent being the ISO system....
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 ratioContrast ratio
The contrast ratio is a property of a display system, defined as the ratio of the luminance of the brightest color to that of the darkest color that the system is capable of producing...
. For example, average Digital Video (DV)
DV
DV is a format for the digital recording and playing back of digital video. The DV codec was launched in 1995 with joint efforts of leading producers of video camcorders....
has a contrast ratio of 45:1, so its exposure range is roughly 5.5 stops. Film
Film
A film, also called a movie or motion picture, is a series of still or moving images. It is produced by recording photographic images with cameras, or by creating images using animation techniques or visual effects...
has an exposure range of approximately 14 stops, currently the highest in motion picture mediums.
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.
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 which transitions, either abruptly or gradually, into...
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
Polycarbonate
PolycarbonatePhysical PropertiesDensity 1.20–1.22 g/cm3Abbe number 34.0Refractive index 1.584–1.586FlammabilityV0-V2Limiting oxygen index25–27%Water absorption – Equilibrium0.16–0.35%Water absorption – over 24 hours0.1%...
, 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.