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is an attribute of visual perception in which a source appears to be radiating or reflecting light. In other words, brightness is the perception elicited by the luminance of a visual target.

Brightness

In color theory, chroma refers to the degree of vividness of a color, or how pure it is compared to its representative on the color wheel. It can also be called saturation, or color intensity.

Chroma or saturation

a law stating that the square of a side of a plane triangle is equal to the sum of the squares of the other two sides minus twice the product of the other sides multiplied by the cosine of the angle between them.

Cosine law

A specified surface sloping up and out from the edge of an approach surface and from a line originating at the end of the inner edge of each approach area, drawn parallel to the runway centerline in the direction of landing.

Transitional surface

is a measure of what proportion of light is transmitted through a turbid medium. Light may be attenuated due to absorption in the medium, or it may be scattered out of the beam.

Transmission

is an angle made by a light ray or wave hitting a surface and the line perpendicular to that surface. An example of an angle of incidence is the angle between a light hitting a table and a line perpendicular to the table.

Angle of incidence

can be defined as the opening in a lens through which light passes to enter the camera.

Aperture

the SI unit of luminous intensity. One candela is the luminous intensity, in a given direction, of a source that emits monochromatic radiation of frequency 540 × 1012 Hz and that has a radiant intensity in that direction of 1/683 watt per steradian.

Candela

or color is the aspect of things that is caused by differing qualities of light being reflected or emitted by them. To see color, you have to have light. When light shines on an object some colors bounce off the object and others are absorbed by it. Our eyes only see the colors that are bounced off or reflected.

Colour

refers to the ' visual sensation correlated with the 'warmth' or 'coolness' of the light emitted by a lamp. The metric used to characterise the colour appearance of the light emitted by a light source is the correlated colour temperature (CCT), expressed in Kelvin (K).

Colour appearance

expressed as a rating from 0 to 100 on the Color Rendering Index (CRI), describes how a light source makes the color of an object appear to human eyes and how well subtle variations in color shades are revealed. ... Color rendering describes how well the light renders colors in objects

Colour rendering

is the ability to detect subtle differences in shading and patterns. Contrast sensitivity is important in detecting objects without clear outlines and discriminating objects or details from their background, such as the ability to discriminate steps covered with a patterned carpet.

Contrast sensitivity

is simply that the lens' focusing ring/scale are physically connected to the optical rangefinder in the camera.

Coupled range-finder

is one where each point on the surface is on a different level than another i.e. it is a jagged surface with varying protrusions and troughs. After reflection from a diffuse surface, light rays aren't parallel to each other but are at an angle and are heading in different directions.

Diffuse surface

is the loss of retinal image contrast as a result of intraocular light scatter, or straylight. It has been described as a reduction of visual acuity caused by light elsewhere in the field of vision (Koch 1989).

Disability glare

is a visual annoyance caused by luminance in the field-of-view that is considerably greater than the luminance to which the visual system is adapted [IES 2011]. It is an immediate occurrence and arises from light sources or luminaires whose luminance is greater than the eye can adapt to. It can also become noticeable after a period of time.

Discomfort glare

is the standard unit for the luminous flux of a light source. It is an SI derived unit based on the candela. It can be defined as the luminous flux emitted into unit solid angle (1 sr) by an isotropic point source having a luminous intensity of 1 candela.

Lumen

- is not capable of having light pass through.

Opaque

the ratio of the amount of radiation absorbed by a surface to the amount of radiation incident upon it.

Optical absorptance

is defined as the ratio of transmitted optical power to the incident optical power for some object, for example an optical system. ... The transmitted power can be affected by interference effects, making the transmittance strongly wavelength dependent.

Optical transmittance

is the light-sensitive tissue lining the back of our eye. Light rays are focused onto the retina through our cornea, pupil and lens. The retina converts the light rays into impulses that travel through the optic nerve to our brain, where they are interpreted as the images we see.

Retina

the decrease in the intensity of a spectral line (an absorption or emission line) with increasing power of the external resonant electromagnetic radiation.

Saturation effect

is the vision of the eye under low-light levels. The term comes from Greek skotos, meaning "darkness", and -opia, meaning "a condition of sight". In the human eye, cone cells are nonfunctional in low visible light.

Scotopic vision

A beam of light can be characterized by its spectral composition, its intensity, its position and direction in space, its phase, and its state of polarization.

Spectral composition

Specular reflection is a type of surface reflectance often described as a mirrorlike reflection of light from the surface. In specular reflection, the incident light is reflected into a single outgoing direction

Specular surface

Reflection of electromagnetic radiation from a rough surface with large irregularities. Also known as mixed reflection.

Spread reflection

is defined as the solid angle which, having its vertex at the center of the sphere, cuts off a spherical surface area equal to the square of the radius of the sphere.

Steradian

is used to describe a medium transmitting most of the light but scattering it more or less so that objects seen through it are blurry with soft contours and without details. The closer the object is to the medium the sharper its image through it.

Translucent -

is defined as the ratio of transmitted optical power to the incident optical power for some object, for example an optical system. For transmission through flat unstructured surfaces, it is the same as the transmissivity.

Transmittance

In the field of optics, transparency (also called pellucidity or diaphaneity) is the physical property of allowing light to pass through the material without appreciable scattering of light.

Transparent

space in which there is no matter or in which the pressure is so low that any particles in the space do not affect any processes being carried on there. It is a condition well below normal atmospheric pressure and is measured in units of pressure (the pascal)

Vacuum

refers to the relative lightness or darkness of a certain area. Value can be used for emphasis. Variations in value are used to create a focal point for the design of a picture.

Value (V) or lightness

is the distance between identical points (adjacent crests) in the adjacent cycles of a waveform signal propagated in space or along a wire.

Wavelength

A continuous group, or range, or wavelengths with an upper limit and a lower limit. In analog terms, bandwidth and channel width are defined as a range of frequencies.

Wavelength band

is the distance between the center of a convex lens or a concave mirror and the focal point of the lens or mirror — the point where parallel rays of light meet or converge.

Focal length

The principle in physics that the effect of certain forces on an object varies by the inverse square of the distance between the object and the source of the force. The magnitude of light, sound, and gravity obey this law, as do other quantities.

Inverse square law

is a form of electromagnetic radiation with a wavelength which can be detected by the human eye. It is a small part of the electromagnetic spectrum and radiation given off by stars like the sun. ... Light exists in tiny energy packets called photons. Each wave has a wavelength or frequency.

Light

is a ray of light that strikes a surface. The angle between this ray and the perpendicular or normal to the surface is the angle of incidence. The reflected ray corresponding to a given incident ray, is the ray that represents the light reflected by the surface.

Light incident

a measure of the ability of an object to absorb radiation, equal to the ratio of the absorbed radiant flux to the incident flux. Absorptance of the surface of a material is its effectiveness in absorbing radiant energy like light and heat. It is the ratio of the absorbed to the incident radiant power. This should not be confused with absorbance and absorption coefficient

Absorptance

is the process of adjusting the focus distance of an optical instrument to the object which is to be viewed.

Accommodation

Clearness, sharpness of a sensory function, e.g., visual acuity

Acuity

is the moving of the lens elements until the sharpest possible image is achieved. Depending on the distance of the subject from the camera, the focusing elements have to be set a certain distance from the camera's sensor to form a clear image. A typical autofocus sensor uses a charge-coupled device (CCD).

Focusing

a small depression in the retina of the eye where visual acuity is highest. The center of the field of vision is focused on this region, where retinal cones are particularly concentrated.

Fovea

- is defined as the number of times an event occurs per unit of time. ... Frequency is the number of times a point on a wave passes a fixed reference point in one second. The period or duration of time of a cycle of a wave is the reciprocal (1 divided by) of frequency

Frequency

is difficulty of seeing in the presence of bright light such as direct or reflected sunlight or artificial light such as car headlamps at night. ... Glare is caused by a significant ratio of luminance between the task (that which is being looked at) and the glare source.

Glare

has uniform properties throughout its volume. That is it does not have lumps of different stuff in it. An isotropic medium has similar properties in any direction of travel for waves through that medium

Homogeneous medium

both a color and a shade of a color. Green is a hue, and turquoise is a hue of both green and blue.

Hue -

measures the sensitivity of the image sensor. The same principles apply as in film photography - the lower the number the less sensitive your camera is to light and the finer the grain. ... By choosing a higher ISO you can use a faster shutter speed to freeze the movement.

ISO rating

is the total luminous flux incident on a surface, per unit area. It is a measure of how much the incident light illuminates the surface, wavelength-weighted by the luminosity function to correlate with human brightness perception.

Illuminance

the intensity of light emitted from a surface per unit area in a given direction.

Luminance

is the measure of brightness of a light source in terms of energy being emitted. Luminous flux, in SI units, is measured in the lumen (lm). It is a measurement of energy released in the form of visible light from a light-producing source.

Luminous flux

is a measure of the wavelength-weighted power emitted by a light source in a particular direction per unit solid angle, based on the luminosity function, a standardized model of the sensitivity of the human eye. The SI unit of luminous intensity is the candela (cd), an SI base unit.

Luminous intensity

the SI unit of illuminance, equal to one lumen per square meter.

Lux

In physics, monochromatic describes light that has the same wavelength, so it is one color.

Monochromatic

A unit of measurement of luminance, or the intensity of visible light, where one nit is equal to one candela per square meter.

Nit

a system of quantities that characterize light in the process of its emission, propagation, and conversion—for example, such processes as reflection and transmission. Photometric quantities are determined with respect to the average light-adapted human eye.

Photometric quantities

is the vision of the eye under well-lit conditions (luminance level 10 to 108 cd/m2 ). In humans and many other animals, photopic vision allows color perception, mediated by cone cells, and a significantly higher visual acuity and temporal resolution than available with scotopic vision

Photopic vision

a glass or other transparent object in prism form, especially one that is triangular with refracting surfaces at an acute angle with each other and that separates white light into a spectrum of colors. In Geometry, it is a polyhedron, with two parallel faces called bases. The other faces are always parallelograms. The prism is named by the shape of its base

Prism

is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes electromagnetic radiation such as radio waves, visible light, and x-rays.

Radiation

is defined as the ratio of reflected radiant flux (optical power) to the incident flux at a reflecting object - for example, an optical component or system. ... The reflectance simply quantifies the amount of light getting back into the half space of the incoming light.

Reflectance