Textbook Notes (270,000)
CA (160,000)
SFU (5,000)
PSYC (1,000)
Chapter 10

PSYC 303 Chapter Notes - Chapter 10: Illuminance


Department
Psychology
Course Code
PSYC 303
Professor
Thomas Spalek
Chapter
10

This preview shows pages 1-3. to view the full 10 pages of the document.
Object:individualentities
Scene:objectsandsurfacesinrelationtooneanother
TheProblemofVisualScenePerception
Image:thepatternoflightreflectedfromobjects
● canbethoughtofasa2Darray,witheachpointasthetotaldensityoflight
(brightness)anditswavelength(hue)
● brightnessandhuedeterminedby:
Lightsource:thedirectionandintensityofthelightproducingregionsinthe
environment
Surfacereflectance:thevariousobjectsthatcomeintocontactwiththelight;
someabsorblightfromoneregionofthewavelengthspectrumthanotherregions,
leadingtotheperceptionofacoloredsurface
Surfaceorientation:determinedwithreferencetoanimaginarylineperpendicularto
thesurface,thesurfacenormal
Viewingposition:therelationshipbetweentheviewerandthescene
Thesefouraspectsoftheviewingsituationdeterminethedistributionoflightintheimage
thatisavailabletotheviewer.Butthisdoesnotgiveaprecisedescriptionoftheworldand
theobjectswithinit.Theretinalimagecouldbeproducedbyaninfinitenumberofscenes.
DavidMarr
Computationalvision:equalemphasisitgivestoresearchfindingsinhumanvision,
neuroscienceandcomputersimulations
● threelevelsofunderstanding(mostabstracttoconcrete)thatcannotbereducedto
another:
○ computationallevelattempttostateexactlywhatthevisualproblemisthat
needstobesolved
○ algorithmiclevelspecifiesvariouswaysthattheproblemcouldbesolvedin
principle
○ implementationleveldescribestheactualequipment(neuronsorsilicone
chips)thatareusedtocomputethealgorithmandaccomplishthetask
RecoveringtheThirdDimension
Ifthreeofthefourlawsaremeasured/known,thenthefourthcanbecalculatedvia
geometry.
Visualillusions:guessesmadebythevisualsystemaboutoneofthescenefactorsis
inappropriate
Scenesarelitfromabove
Shading:asmoothvariationintheluminanceofanimage

Only pages 1-3 are available for preview. Some parts have been intentionally blurred.

● canbecurved,duetogradation(ofmaterial)orcastbyotherobjects
Iftheobjectislitfromabove,theshadingislighttodark(convex/pimple)andviseversa
(concave/dimple).
Surfacesaregenerallyconvex
Ahollowmasklitfromabovewillappearasaconvexfacelitfrombelow.
Objectsareattachedtosurfaces
Thevisualsystemtendstopresumethatobjectsrestonsurfaces,evenwhenthesurfaces
arenotvisible.
Objectsaregenerallyviewedfromabove
Schroederstairsillusionorientationofstairs(tendencytoseefromaboveA)
Agenericviewpoint
Oneofthemostgeneralbiasesofhumanvisionistointerpretarelationbetweentwoor
moreedgesasthoughitwillholdavarietyofpossibleviewpoints.
Genericviewpoint:humanvisiontendstoignoretheselowprobabilitycoincidencesand
focusesinsteadoninterpretationsthatassumeedgerelationsshownintheimageare
generallytrueandwouldholdwhentheobjectwasviewedfromavarietyofdifferentangles
andpositions
PerceptualConstancy
Perceptualconstancy:thatourperceptionsofobjectsandscenesdonotvarynearlyas
muchasthefluctuationsintheimagesofthosesameobjectsandscenes
Sizeconstancy
Asthedistancebetweentheeyeandtheobjectgrowslarger,thesizeoftheretinalimage
growsmaller.
Sizeconstancy:theabilitytoseeanobjectasbeingthesamesizedespitechangesin
objectivedistanceandretinalimagesize.
Sizeconstancyinpictureperception
Certaindepthcuesinpicturesindicatetousthatapictureisflat,but
othercuesprovideimagedepth.
Ponzoillusion:twohorizontallinesofequallengthplacebetweentwo
converginglines

Only pages 1-3 are available for preview. Some parts have been intentionally blurred.

MuellerLyerillusion:twoverticallinesaremarkedwithdifferentarrow
● Whenarrowsarepointingin,themimictheconcavecornersofaroom(appearing
closer,thisshorter)andviseversa
SizeconstancyandtheMoon
Moonillusion:whenthemoonisonthehorizonappearslargerthanwhenthemoonisin
thesky
● onehalfdegreeofavisualangle
● appearssmallerifseenfromupsidedown
Theskyappearstobeaflatteneddomebecauseofthelackofdepthcuesatthehighest
point(zenith).
Shapeconstancy
Shapeconstancy:theperceptionoftheenduringshapeofanobject,despitewide
variationsintheshapethatisprojectedfromthatobjectotoureyes.
Slant:differentdistancestopartsofthesameobject;object’sorientationinspace
Principleaxis:thelongestdimension
Boxalignmentillusion:edgesappeardivergeastheymovetowardsthetopofthepage,
butareactuallyparallel
You're Reading a Preview

Unlock to view full version