The Opsin in humans that is excited by the short Wavelengths in the Visible Range (hence the "S" for short). The typical form has a Peak Wavelength at 420nm, which is a wavelength that excites blue/violet in Color Normals, hence…

Often one channel of a 3D Color Space, such as HSL or HSV. Determines the vibrancy of a color. Equivalent to Chroma or Colorfulness.

A type of Pseudoisochromatic Plate developed by Frenchman D. Schaaff in 1925. Instead of numerals, it is based on the Landolt C (Landolt ring), which is the same principle used in the Colorlite online tests (link). Dechromatized Colorlite Landolt-C style…

In opsins, the Schiff Base is the amino acid that chemically attaches to the Chromophore. In animals, this is believed to always be Lysine-296.

An indicator discovered by Schmidt in [1955] that can identify female carriers of Protan CVD. Protans exhibit Scoterythrous Vision (a darkening of red wavelengths) due to the shift or absence of the L-Opsin. Carriers of a protanopic or protanomalous allele…

From scot- (greek skotos - darkness) and erythro- (greek erythros - red); meaning a darkening (less luminous) of the red portion of the visible spectrum, or likewise, a shortening of the visible spectrum on the red end. This is a…

Scotopic Vision is optimized for dim environments, generally enabled by Rod Cells in vertebrates. With Photopic Vision, they make up both halves of the Duplex Retina. Scotopic Vision is usually used at night by humans or otherwise in dim environments…

The protein component of Rhodopsin. The protein can be paired with two different Chromophores, which results in one of two opsins: Rhodopsin - when paired with Retinal Vitamin A1 has a Peak Wavelength at about 500nm. This form is dominant…

An equal mixture of two Primary Colors for a given Color Space.

A name for a genetic disorder influenced by a gene on a sex chromosome. It generally refers to genes on the X chromosome (therefore mainly synonymous with X-linked) because the X chromosome is larger and contains many more genes than…

A non-technical description of color that supposes "Color" equals Hue (e.g. red, blue, purple, etc.) and shade refers to variants in Saturation and Darkness of each hue. In Colorimetry, the definition of a color involves ALL those parameters and "shade"…

An alteration of an image that tries to convey what colorblind vision is like. Because color vision is a Qualia, it can not be fully accurate to "show what colorblind people see". However, Simulations are very useful at conveying the…

A color that can be excited by a single wavelength of light, also known as Monochromatic Light. All other colors are Extra-spectral Colors.

Instead of typical digital cameras that have sensors that divide an image into 3 bands that mimic humans' trichromatic vision, Spectral Imaging will increase the number of bands so more information is gleaned about the underlying spectral information of the…

The series of Spectral Colors on a Chromaticity Diagram which - along with the Line of Purples - acts as the perimeter for the CIEXYZ Color Space. https://youtu.be/onOrILyPWpw

See Absorption Spectrum.

A subset of Colorimetry that precisely studies color by considering the light always as a Spectrum, and not in a 3-deimensional Color Model as is usually the case in Color Theory.

A measurement of light that plots its Wavelength content, i.e. the energy content as a function of Wavelength. Spectra are used in Spectroscopy, but are generally not considered in most domains of Color Theory, where the 3-D Color Models are…

A Color Space of the RGB Color Model that was developed in 1998. It is still the default Color Space for many digital images (e.g. HDTV). sRGB can be depicted on old CRT Monitors because the Chromaticities of the Primaries…

A Standard Illuminant is a theoretical source of visible light with a very specific, published spectrum. Standard illuminants provide a basis for comparing images or colors recorded under different lighting. For example, most colorblind tests are specified to be used…

A hypothetical visual system defined as mathematical equations (Color Matching Functions) intended to represent the typical human. The Standard Observer is used as a universal technical definition of the perceptual effects of light stimuli on humans, specifically as part of…

A type of PIP devised by Hiroshi Ichikawa in 1978. There are 2 editions, SPP1 & SPP2, plus SPP3, which is just a combination of the other two. They test for blue-yellow & red-green CVD, but they are much less…

The original pseudoisochromatic plate test for color vision, released in 1876. At the time, it was a massive improvement to the most common color vision test at the time: Holmgren's Wool. Foremost, it was based on the burgeoning Opponent Process…

A tetrachromat who not only expresses the prerequisite photoreceptors for Tetrachromacy - as with a Weak Tetrachromat - but also has true 4-dimensional color vision as confirmed by Behavioral Tests.

A task that asks an individual to name the color of a word (not to read the word). When the word matches the color (top of the image below), individuals perform well. When the word does not match the color…