exposure

exposure

1. Archit the position or outlook of a house, building, etc.; aspect

2. Mountaineering the degree to which a climb, etc. is exposed (see exposed (sense 4))

3. Photog

a. the act of exposing a photographic film or plate to light, X-rays, etc.

b. an area on a film or plate that has been exposed to light, etc.

c. (as modifier): exposure control

4. Photog

a. the intensity of light falling on a photographic film or plate multiplied by the time for which it is exposed

b. a combination of lens aperture and shutter speed used in taking a photograph

5. See indecent exposure

Exposure

The area on any roofing material that is left exposed to the elements.

Exposure

 

in photography, the quantity of illumination H (a photometric quantity), which serves as an evaluation of the surface density of the luminous energy Q. It determines the effect of optical radiation on the photographic material used.

In the general case, H = dQIdA = ∫Edt, where A is the illuminated area, E is the illuminance, and I is the duration of irradiation (exposure time). If E is a constant, then H = Et. In the SI system (seeINTERNATIONAL SYSTEM OF UNITS), exposure is expressed in lux-seconds (lx-s). Beyond the limits of the visible portion of the radiation spectrum, the quantity used is the energy exposure, which is the product of the irradiance and the duration of irradiation; it is expressed in joules per m² (J/m²).

It is convenient to use the concept of exposure if the effect of radiation is cumulative over time (in photography as well as, for example, in photobiology). The concept is widely used in work with nonoptical and even corpuscular radiation, such as X rays and gamma rays (where the exposure is defined as the product of the surface density of the radiation flux and the duration (), as well as streams of electrons and other particles (where the exposure is equal to the product of the radiation dose rate and t). (See alsoSENSITOMETRY and CHARACTERISTIC CURVE.)

A. L. KARTUZHANSKH

exposure

[ik′spō·zhər]

(building construction)

The distance from the butt of one shingle to the butt of the shingle above it, or the amount of a shingle that is seen.

(graphic arts)

The act of permitting light to fall upon a photosensitive material.

(medicine)

The state of being open to some action or influence that may affect detrimentally, as cold, disease, or wetness.

(meteorology)

The general surroundings of a site, with special reference to its openness to winds and sunshine.

(nucleonics)

The total quantity of radiation at a given point, measured in air.

The cumulative amount of radiation exposure to which nuclear fuel has been subjected in a nuclear reactor; usually expressed in terms of the thermal energy produced by the reactor per ton of fuel initially present, as megawatt days per ton.

(optics)

light exposure radiant exposure

shake

A thick wood shingle, usually formed either by hand-splitting a short log into tapered radial sections or by sawing; usually attached in overlapping rows on wood sheathing, 1 as a covering for a roof or wall.

exposure

i. The total quantity of light received per unit area on a sensitized plate or film. It may be expressed as the product of the light intensity and the exposure time.
ii. The act of exposing a light-sensitive material to a light source.
iii. One individual picture of a strip of photographs, usually called a frame.

exposure

(1) The degree to which information can be accessed using authorized or unauthorized methods. See penetration test and risk analysis.

(2) In a camera, the amount of light that reaches the film (analog) or CCD or CMOS sensor (digital). The exposure is achieved by the sum of the shutter speed, aperture (f-stop) and ISO setting. See shutter speed, f-stop and ISO speed.