Lecture 25

Question 1

what can alter the lightness perception of an object

Answer 1

the background colour

Question 2

Mach bands

Answer 2

False impression of a narrow dark band immediately to the left and a narrow light band immediately to the right of each boundary

Question 3

the way that photoreceptors converge onto bipolar cells and RGCs accounts for

Answer 3

• acuity

- light sensitivity

Question 4

snellen chart

Answer 4

• herman snellen
• 1862
• asked to read 5 stroke letter s as they get smaller

Question 5

what is measurement or normal vision

Answer 5

20/20

Question 6

what is legal blindness

Answer 6

20/200

Question 7

visual angle

Answer 7

the angle subtended by an object on the retina

Question 8

what is the smallest resolvable gratins

Answer 8

0.017 degrees

Question 9

To be able to see the detect that there is white and

Answer 9

need to have photoreceptors that respond to light in the dark and light area

Question 10

spatial frequency

Answer 10

number of times a pattern repeats in each unit of space

Question 11

varying frequency alters level of

Answer 11

details

Question 12

varying amplitude alters level of

Answer 12

contrast

Question 13

contrast threshold

Answer 13

smallest amount of contrast required to detect a pattern

Question 14

nyquist limit

Answer 14

highest spatial frequency that a photoreceptor array can theoretically sample (60 cycles/degree)

Question 15

Contrast of 1% means

Answer 15

the average intensity was 100 photons the light bar would have to be 101 photons and the dark bar is 99 photons (varying 1 from the average)

Question 16

CSF

Answer 16

human contrast sensitivity curve

Question 17

factors that affect the CSF (3)

Answer 17

adaptation level
age
disease

Question 18

as you age what happens to optic and neural factors

Answer 18

optical and neural factors reduce high frequency cut off
(People who are older are able to see less spatial details (as you age pupils get smaller so less light enters the retina)

Question 19

have infants mechanisms to encode high spatial frequencies fully matured?

Answer 19

no

Question 20

myopia

Answer 20

blurred retinal image

most severe at high frequency

Question 21

cataract

Answer 21

broad decrease in sensitivity
due to opacity so light isnt passing through as easily
looking more at scotopic visual system

Question 22

MS and vision

Answer 22

inflammation of optic nerve, demyelinating disease, if myelin around optic nerve starts breaking down than info from optic nerve can’t go to rest of the brain, outer axons affected first which is why lose low spatial frequency detection first