Lecture 1

Question 1

Less refrangible rays (less refractable) are more ___ in color, while more refrangible rays are more ___ in color

Answer 1

LESS refracted: red

MORE refracted: violet

Question 2

• formula for electromagnetic radiation?

- Energy is proportional to _____ (which variable?)

Answer 2

frequency = (speed of light/wavelength)

-energy: proportional to frequency (E=hv, where v=frequency, h=planck’s constant)

Question 3

Color deficient individuals lacking L cones see red as (lighter/darker) than color deficient pts lacking M cones

Answer 3

L cones missing - can’t discriminate R/G - red seems DARKER

Question 4

what color was not represented in Newton’s color circle?

Answer 4

purple

Question 5

Name of the first man who tried to associate color vision with physiology? i.e. who was first to propose the concept of CVD?

Answer 5

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)

Question 6

The short, middle, and long-wavelength cones are maximally sensitive to which wavelengths, respectively?

Answer 6

S: 427, M: 530, L: 557 (560)

Question 7

Palmer was the first to talk about color deficiencies, but ____ was the first to analyze it because he himself was color deficient.

Answer 7

Dalton. John Dalton - first to notice that certain flowers didn’t look the same to him as they did to others

Question 8

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?

Answer 8

Helmholtz; line of purples. Combinations of complimentary colors produces perfect WHITE light.

GREEN - has no perfect, single compliment. Requires mixture of purples.

Question 9

first to discover that each monochromatic light can be reproduced by the three primaries in the right proportions

Answer 9

Mawell. Clark Maxwell.

Question 10

HERING noted that WHICH two pairs of colors can NOT be seen together?

Answer 10

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

Question 11

which theory is correct: the 1) trichromatic theory by Young/Helmholtz or the 2) color opponency theory by Hering?

Answer 11

both. trick question.

Question 12

what are the three steps in the perception of light?

Answer 12

• wavelength detection
• wavelength discrimination
• color appearance

Question 13

name the five photopigments, what they’re associated with, wavelength they’re sensitive to, and whether they’re involved in light perception

Answer 13

rhodopsin - rods - 507nm
cyanolab - S-cones - 427nm
chlorolab - M-cones - 530nm
erythrolab - L-cones - 560nm
melanopsin - no visual role (sleep/wake?)

Question 14

T/F: Different proportions of L and M cones can be present, and different people will still have the same color vision.

Answer 14

True…that’s usually the case

Question 15

Define: metamer.

-then give an example.

Answer 15

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

Question 16

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)

Answer 16

Christiaan Huygens

Question 17

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?

Answer 17

complimentary

GREEN had complimentaries not on spectrum - there were the PURPLES (NOT monochromatic; require at least 2 wavelengths)

Question 18

Who proposed the COLOR OPPONENT THEORY, stating that there are certain colors that simply CAN’T be seen together? What are those colors?

Answer 18

Hering (color opponent theory) - compliments Young+Helmholtz’ (trichromatic theory)

-CAN’T see: red/green together, or blue/yellow together

Question 19

Light detection is achieved by HOW MANY photoreceptors? i.e., ___ photopigments (since each PR has a unique pigment) are responsible for DETECTING light?

Answer 19

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

Question 20

which technique demonstrates the DIFFERENCE of light reflected back (vs how much was absorbed) Does a bleached or non-bleachesd retina reflect more light?

Answer 20

reflection densitometry - a BLEACHED retina REFLECTS more (b/c photopigment is temporarily unavailable to absorb wavelengths)

Question 21

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?

Answer 21

MSP -microspectrophotometry.

Question 22

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?

Answer 22

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)

Question 23

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?

Answer 23

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

Question 24

luminance of our system has about a ___ (number) log unit difference

Answer 24

16x

i.e. allows us to see 16x brighter/wide range very dim to very bright

Question 25

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?

Answer 25

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

Question 26

wavelength range (10^xx) for:

• scotopic conditions:
• mesopic conditions:
• photopic conditions:

Answer 26

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]

Question 27

SCOTOPIC spectral sensitivity graph says we’re optimally sensitive to light of ~___nm (assuming we’re dark-adapted)

Answer 27

505nm

Question 28

What term describes the difference b/w the scotopic and photopic spectral sensitivity fxn?

Answer 28

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)