________ is defined as the brightness of the light at which teh patient correctly detects the light 50% of the time.
Threshold
______ is the probability that the test will accurately detect thse patients with the diesease.
Sensitivity
______ is the probability the test will accurately detect those patients without the disease
Specificity
_________ is the probabilty that the patient has the disease if the test is positive
Positive predictive value (PPV)
_________ is the probability the patient does not have the disease if the test is negative
Negative predictive value (NPV)
________ is the energy per second produced by a light source (in watts, W)
Radiant Power
__________ is the energy per second (or radiant power) in a given direction (in watts per solid angle, W/Ω); used to describe point sources
Radiant intensity
__________ is the radiant intensity per projected area of a light source; is used to describe extended sources that have an area
Radiance
_________ is the radiant power per unit area of a surface; it deals with the amount of light that reaches a given target
Irradiance
What is the difference btw Radiometry and Photometry
Radiometry is the physical (measureable) property of light.
Photometry is the perception of light.
Analogous to radiant power; Visual system’s response to light
Luminous power (lumens)
Luminous power in a given direction; deals with point sources
Luminous intensity (lumens per solid angle = candela, I/Ω)
The luminous intensity per projected area of the light source; deals with spatially extended sources. Luminance can also be measured in foot-lamberts, with one foot lambert =3.43 nits
Luminance (candelas per square meter, c/m2, sometimes called nits)
The luminous power per unit area of a surface as with irradiance, illuminance deals with light striking or falling upon a target object. Illuminance can also be measured in foot-candles, which are lumens per square foot. One foot candle = 10.8 lux
Illuminance (lumens per square meter or lux, l/m2)
When a neutral density filter palced in front of one eye, the neural response of the visual cortex is slowed compared to the fellow eye without a neutral density filter. As a result the pendulum (which is moving along one plane [back and forth]) appears to move in an ellipse.
Pulfrich phenomenon
If the neutral density filter is placed over the left eye the pendulum appears to move clockwise
If the neutral density filter is placed over the right eye the pendulum appears to move counter clockwise
A surface that shows the same luminance from every viewing angle i.e., the surface scatters light equally in all directions (e.g. paper with a matte finish)
Lambert surface
A surface that unequally scatters light in different directions e.g. a shiny piece of silver
Specular surface
opposite of a lambert surface
A shift from photopic conditions to scotopic conditions switch which wavelengths the visual system is more sensitive to. Photopic is more sensitive to longer wavelengths, Scoptic is more sensitive to shorter wavelengths. This translates to color red being harder to see at night.
Purkinjie shift
The photochromatic interval is zero at _________ because the photopic and scotopic systems are equally sensitive to this wavelength. AKA the point of equal sensitivity.
650nm
This equation states that as your background brightness increases your stimulus brightness must also increase in order for it to be percieved. It also makes the assumption that photopigment is the sole caus e of dark adaptation.
Dowling-Rushton Equation
How long is the half life of rhodopsin
5 minutes
_______ vision is characterized by great sensitivity and poor resolution due to larger pixels
scotopic
______ vision is characterized by poor sensitivity and great resolution due to smaller pixels
Photopic
________ law describes the relationship between the intensity and the area of the stimulus that is below the threshold for spatial summation.
Ricco’s Law
