Related Experiment Video
Updated: Aug 7, 2026
09:29
A Standardized Obstacle Course for Assessment of Visual Function in Ultra Low Vision and Artificial Vision
Published on: February 12, 2014
Psychophysical measurements concerning the range of visual perception
Pflugers Archiv : European Journal of Physiology
|July 1, 1980
Summary
The just noticeable difference (jnd) in brightness perception is consistent across scotopic and extrafoveal conditions, following a power function model. This finding extends previous research on visual perception and brightness scaling.
Area of Science:
- Visual Perception
- Psychophysics
- Photometry
Background:
- Previous research established a model for the just noticeable difference (jnd) in brightness (delta L = delta Ls + bLc) for foveal, photopic conditions.
- Parameters delta Ls and b were found to be power functions of adapting luminance (LU).
Purpose of the Study:
- To investigate the jnd of brightness under scotopic background luminances and extrafoveal viewing conditions.
- To determine if the previously established model applies to these new conditions.
- To analyze the scaling of brightness perception across different adaptational levels and viewing areas.
Main Methods:
- Presented adjacent semicircular test fields with differing luminances (L and L + delta L) on an adapting field (LU).
- Measured jnd under scotopic conditions and for extrafoveal observations (6 and 12 degrees temporal).
- Analyzed data using the model delta L = delta Ls + bLc and power functions.
Main Results:
- Under scotopic conditions, foveal jnd was largely independent of LU but dependent on L, fitting a consistent curve.
- Extrafoveal results also fit the delta L = delta Ls + bLc model, with delta Ls and b as power functions of LU across a wide luminance range (0.001 to 100 cd/m2).
- Parameters delta Ls and b were power functions of LU, and 'c' increased with log L (1.1-1.5).
- The sum of jnd-steps (dynamic characteristic) differed between fovea and periphery.
- Fechner scaling (static characteristic) showed similarity to the Stevens power function.
Conclusions:
- The established model for brightness jnd is applicable to both scotopic and extrafoveal conditions.
- Brightness perception exhibits distinct dynamic characteristics for foveal versus peripheral vision.
- Fechnerian and power scaling laws for brightness show notable convergence.
Related Concept Videos
01:20Anatomy of the Eyeball
The eye is a spherical, hollow structure composed of three tissue layers. The outer layer — the fibrous tunic, comprises the sclera — a white structure — and the cornea, which is transparent. The sclera encompasses some of the ocular surface, most of which is not visible. However, the 'white of the eye' is distinctively visible in humans compared to other species. The cornea, a clear covering at the front of the eye, enables light penetration. The eye's middle layer, the vascular tunic,...
01:22Photoreceptors and Visual Pathways
At the molecular level, visual signals trigger transformations in photopigment molecules, resulting in changes in the photoreceptor cell's membrane potential. The photon's energy level is denoted by its wavelength, with each specific wavelength of visible light associated with a distinct color. The spectral range of visible light, classified as electromagnetic radiation, spans from 380 to 720 nm. Electromagnetic radiation wavelengths exceeding 720 nm fall under the infrared category, whereas...
01:15Depth Perception and Spatial Vision
Depth perception is the ability to perceive objects three-dimensionally. It relies on two types of cues: binocular and monocular. Binocular cues depend on the combination of images from both eyes and how the eyes work together. Since the eyes are in slightly different positions, each eye captures a slightly different image. This disparity between images, known as binocular disparity, helps the brain interpret depth. When the brain compares these images, it determines the distance to an object.
01:26Visual System
Light enters the eye through the cornea, a transparent, dome-shaped surface covering the surface of the eyeball that helps to direct and focus incoming light. This light is then channeled toward the pupil, an adjustable opening whose size is controlled by the iris. The iris, a pigmented muscle, regulates the amount of light entering the eye by contracting or dilating the pupil, thereby ensuring optimal light levels for clear vision.
Once through the pupil, the light passes through the lens, a...
Once through the pupil, the light passes through the lens, a...
01:24Color Vision
Color perception begins in the retina, the light-sensitive layer at the back of the eye. Two main theories explain how colors are seen: the trichromatic theory and the opponent-process theory. The trichromatic theory, proposed by Thomas Young in 1802 and extended by Hermann von Helmholtz in 1852, suggests that color vision is based on three types of cone receptors in the retina. These cones are sensitive to different but overlapping ranges of wavelengths corresponding to red, blue, and green.
01:12Perceptual Constancy
Perceptual constancy is the ability to recognize that objects remain consistent and unchanged even when their appearance varies due to changes in sensory input. There are four main types of perceptual constancy: size constancy, shape constancy, color constancy, and brightness constancy.
Size constancy is the recognition that an object remains the same size, even when its image on the retina changes. For instance, a bus is perceived to be large enough to carry people, even if it looks tiny from...
Size constancy is the recognition that an object remains the same size, even when its image on the retina changes. For instance, a bus is perceived to be large enough to carry people, even if it looks tiny from...