Lecture 1 Flashcards
Less refrangible rays (less refractable) are more ___ in color, while more refrangible rays are more ___ in color
LESS refracted: red
MORE refracted: violet
- formula for electromagnetic radiation?
- Energy is proportional to _____ (which variable?)
frequency = (speed of light/wavelength)
-energy: proportional to frequency (E=hv, where v=frequency, h=planck’s constant)
Color deficient individuals lacking L cones see red as (lighter/darker) than color deficient pts lacking M cones
L cones missing - can’t discriminate R/G - red seems DARKER
what color was not represented in Newton’s color circle?
purple
Name of the first man who tried to associate color vision with physiology? i.e. who was first to propose the concept of CVD?
George Palmer (1700s) - first to propose concept of color deficiencies. Included yellow lamps w/ blue filters to simulate natural daylight (began industrial revolution d/t ability of night shift work)
The short, middle, and long-wavelength cones are maximally sensitive to which wavelengths, respectively?
S: 427, M: 530, L: 557 (560)
Palmer was the first to talk about color deficiencies, but ____ was the first to analyze it because he himself was color deficient.
Dalton. John Dalton - first to notice that certain flowers didn’t look the same to him as they did to others
First to discover that each color has a color opponent, that that green’s opponent color formed the line of ____
-For this reason, which is the ONLY color that requires a mixture of complimentary colors in order to produce a perfect white color after being mixed?
Helmholtz; line of purples. Combinations of complimentary colors produces perfect WHITE light.
GREEN - has no perfect, single compliment. Requires mixture of purples.
first to discover that each monochromatic light can be reproduced by the three primaries in the right proportions
Mawell. Clark Maxwell.
HERING noted that WHICH two pairs of colors can NOT be seen together?
Blue/yellow
Red/green
-neurons in the visual system elicit either red OR green responses, or blue OR yellow, but never a combination - premises of color opponency theory
which theory is correct: the 1) trichromatic theory by Young/Helmholtz or the 2) color opponency theory by Hering?
both. trick question.
what are the three steps in the perception of light?
- wavelength detection
- wavelength discrimination
- color appearance
name the five photopigments, what they’re associated with, wavelength they’re sensitive to, and whether they’re involved in light perception
rhodopsin - rods - 507nm cyanolab - S-cones - 427nm chlorolab - M-cones - 530nm erythrolab - L-cones - 560nm melanopsin - no visual role (sleep/wake?)
T/F: Different proportions of L and M cones can be present, and different people will still have the same color vision.
True…that’s usually the case
Define: metamer.
-then give an example.
METAMER: two colors that look absolutely IDENTICAL to the eye, but have different spectral composition (i.e. must pass thru PRISM) to determine whether yellow is made up of green and orange, or if it’s a result of a monochromatic light being passed thru a prism. One PURE, one MIXED combo
Name the guy responsible for findings that PAIRS of monochromatic light could be combined to form WHITE? (opposed Newton’s theory saying that ALL colors were required)
Christiaan Huygens
Hermann-Helmholtz proposed that every color has a ____ color that produces white when mixed, but certain shades of ____ had a complimentary colors NOT on the spectrum…what were these colors?
complimentary
GREEN had complimentaries not on spectrum - there were the PURPLES (NOT monochromatic; require at least 2 wavelengths)
Who proposed the COLOR OPPONENT THEORY, stating that there are certain colors that simply CAN’T be seen together? What are those colors?
Hering (color opponent theory) - compliments Young+Helmholtz’ (trichromatic theory)
-CAN’T see: red/green together, or blue/yellow together
Light detection is achieved by HOW MANY photoreceptors? i.e., ___ photopigments (since each PR has a unique pigment) are responsible for DETECTING light?
FOUR
S-cones: cyanolabe: 427
M-comes: chlorolabe: 530
L-cones: erythrolabe: 560
Rods: RHODOPSIN: 507nm
-melanopsin (5th PR) exists, but has NO ROLE in the detection of light
which technique demonstrates the DIFFERENCE of light reflected back (vs how much was absorbed) Does a bleached or non-bleachesd retina reflect more light?
reflection densitometry - a BLEACHED retina REFLECTS more (b/c photopigment is temporarily unavailable to absorb wavelengths)
Photopigment absorbtion spectra can also be determined using what second method, where it estimates the absorbtion of light as it stimulates a SINGLE cone from an EXCISED retina?
MSP -microspectrophotometry.
Photopigment molecules (opsins) are READY to react to light when the opsin is bound to a chromophore w/ WHAT configuration?
-that configuration undergoes transformation to WHAT new configuration when activated by light?
11-cis-retinal
ALL-trans-retinal (ALL REACT!!!)
All-trans undergoes the RETINOID cycle to be converted back to 11-cis (so it will be ready to be bound again)
WHERE (in what layer) of the retina is ALL-trans (activated form) converted back to 11-cis? Where does it reside when it’s ready to be hit by light again?
conversion of all-trans back to 11-cis: RPE (closer to choroid)
-11-cis stored in the OS, where it’s ready to be hit again by more light
luminance of our system has about a ___ (number) log unit difference
16x
i.e. allows us to see 16x brighter/wide range very dim to very bright
visual perception under DAYLIGHT causes us to see (long/short) wavelengths as being brighter. How about MOONLIGHT? Who figured this out? WHY is this the case?
Day: LONG (red) is brighter
Moon: SHORT (blue) is brigher
Purkinje did! Why? Photopic system has a LOW sensitivity for SHORT wavelengths (hence, blue is dimmer, making red seem brighter) - deals w/ peak spectral sensitivity of 555nm
-basis of two separate SYSTEMS (photopic/scotopic) that operate under different brightness conditions
wavelength range (10^xx) for:
- scotopic conditions:
- mesopic conditions:
- photopic conditions:
scotopic: 10^-6 - 10^-2 (approx)
mesopic: 10^-1 - 10^1 (ish)
photopic: 10^1 - 10^10
SO: -6-(-2), -1-(+1), 1-10 [cd/m^2]
SCOTOPIC spectral sensitivity graph says we’re optimally sensitive to light of ~___nm (assuming we’re dark-adapted)
505nm
What term describes the difference b/w the scotopic and photopic spectral sensitivity fxn?
photochromatic interval: interval where we can’t perceive COLOR, but we can perceive LIGHT (RODS have higher peak/have higher sensitivity, but can’t perceive color)
