Presentation is loading. Please wait.

Presentation is loading. Please wait.

January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 20021 Perception of Brightness The physics and psychophysics…

Published by Modified over 9 years ago

Similar presentations

Presentation on theme: "January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 20021 Perception of Brightness The physics and psychophysics…"— Presentation transcript:

1 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 20021 Perception of Brightness The physics and psychophysics…

2 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 20022 Perception of brightness psychophysics: relate psychological measures to physical ones perception of brightness is one of the simplest aspects of vision to study what is the relationship between –psychological perception of brightness –physical parameters of light intensity

3 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 20023 Units:watts Property: intensity = (amplitude) 2 = energy/sec = power Physical measures 1. Light Ray

4 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 20024 Units: watts, lumens (1 lumen ≈ 1mW) Property: radiance = total energy / sec (all light produced) Physical measures 2. Light Source 120 volt, 100 watt "standard" bulb produces ~1750 lumens

5 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 20025 Units:watts/m 2, lumens/m 2 Property: irradiance = power / area (total falling on surface from all directions) Physical measures 3. Light Received

6 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 20026 Units: fraction (between 0 and 1) - 0 = total absorption (black) - 1 = total reflection (white) Property: reflectance (albedo) = outgoing light incoming light Physical measures 4. Light Reflected

7 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 20027 Psychological measures Brightness subjective estimate of… –intensity? –radiance? –irradiance? –reflectance? of light from a light source or from a reflecting surface

8 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 20028 Psychological measures Lightness subjective estimate of the whiteness of a surface: –intensity? –radiance? –irradiance? –reflectance?

9 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 20029 Relating physical and psychological measures 1.brightness versus intensity 2.brightness versus wavelength 3.brightness depends on surroundings 4.lightness depends on illumination

10 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200210 Relating physical and psychological measures 1.brightness versus intensity 2.brightness versus wavelength 3.brightness depends on surroundings 4.lightness depends on illumination

11 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200211 Brightness versus intensity standard light at fixed intensity test light with adjustable intensity adjust power of test until just begins to differ just noticeable difference: JND

12 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200212 StandardTest A just noticeable difference (JND) at 11W 1 W above standard Brightness versus intensity

13 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200213 Forced-choice Response A bit more rigorous Q: brighter light on left or right?

14 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200214 Forced-choice Response A bit more rigorous Q: brighter light on left or right?

15 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200215 Forced-choice Response A bit more rigorous Q: brighter light on left or right?

16 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200216 Forced-choice Response A bit more rigorous Q: brighter light on left or right?

17 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200217 Forced-choice Response A bit more rigorous Q: brighter light on left or right?

18 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200218 Forced-choice Response A bit more rigorous Q: brighter light on left or right?

19 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200219 Forced-choice Response A bit more rigorous Q: brighter light on left or right? Analyse accuracy of response versus intensity of lights

20 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200220 Psychometric function accuracy (probability correct) as a function of intensity of test light Probability of correct response

21 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200221 Psychometric function accuracy (probability correct) as a function of intensity of test light

22 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200222 Psychometric function accuracy (probability correct) as a function of intensity of test light

23 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200223 For I = 10 W, jnd  I = 0.8W For I = 30 W, jnd  I = 2.5W For I = 50 W, jnd  I = 4.0W  I / I =.08 Weber’s Law for a large range of intensities:  I / I = constant

24 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200224 Weber’s Law for a large range of intensities:  I / I = k k = Weber constant different value of k for different senses –light intensity: k = 0.08 –sound intensity: k = 0.05

25 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200225 Relating physical and psychological measures 1.brightness versus intensity 2.brightness versus wavelength 3.brightness depends on surroundings

26 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200226 Brightness depends on wavelength Light 1: at one wavelength Light 2: at different wavelength Adjust power of second light until its brightness is the same as the first

27 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200227 Brightness depends on wavelength Light 1: at one wavelength Light 2: at different wavelength Adjust power of second light until its brightness is the same as the first

28 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200228 Brightness depends on wavelength Light 1: at one wavelength Light 2: at different wavelength Adjust power of second light until its brightness is the same as the first

29 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200229 Brightness depends on wavelength Light 1: at one wavelength Light 2: at different wavelength Adjust power of second light until its brightness is the same as the first

30 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200230 Result: Luminosity Curve different wavelengths have different luminosities some wavelengths are brighter than others

31 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200231 Luminosity Curve wavelength (nm) Luminosity 1.0 0.8 0.6 0.4 0.2 0 400500600700 Sensitivity in daylight

32 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200232 wavelength (nm) Luminosity 1.0 0.8 0.6 0.4 0.2 0 400500600700 Sensitivity in daylight Sensitivity at night Luminosity Curve

33 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200233 wavelength (nm) Luminosity 1.0 0.8 0.6 0.4 0.2 0 400500600700 Sensitivity in daylight Sensitivity at night Luminosity Curve Photopic vision (cones)

34 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200234 wavelength (nm) Luminosity 1.0 0.8 0.6 0.4 0.2 0 400500600700 Sensitivity in daylight Sensitivity at night Purkinje shift Luminosity Curve Photopic vision (cones)

35 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200235 Pulfrich Effect

36 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200236 Relating physical and psychological measures 1.brightness versus intensity 2.brightness versus wavelength 3.brightness depends on surroundings 4.lightness depends on illumination

37 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200237 Simultaneous brightness contrast: two squares of the same intensity

38 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200238 Simultaneous brightness contrast: left one looks brighter

39 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200239 Simultaneous brightness contrast: pattern increases difference

40 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200240 Recall structuralism perception of each patch = atom atoms are independent perception of patch should not be influenced by surroundings but it is… Visual system always takes context into account –visual intelligence

41 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200241 Is this lateral inhibition? reduction of signal when neighboring areas are active

42 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200242 Context matters! simultaneous brightness contrast –affected by immediate surrounding and –context further away the right context can make this effect even stronger…

43 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200243 The snake illusion (Adelson)

44 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200244 Relating physical and psychological measures 1.brightness versus intensity 2.brightness versus wavelength 3.brightness depends on surroundings 4.lightness depends on illumination

45 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200245 Lightness depends on illumination one patch (on a simple background) estimate lightness of patch when different illumination is used

46 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200246 Result? Lightness unaffected by illumination –lightness constancy Visual system computes lightness as a ratio = intensity of light from square intensity of light from background

47 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200247 Lightness is invariant under illumination level Thus, obtain an estimate that is a property of the world (object surface) –doesn’t change with lighting rather than the image (light on retina) –does change with lighting

48 January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 200248 Finally What was the purpose of this presentation? Which question remains unanswered?

Download ppt "January 22, 2002Psyc202-005, Term 2, Copyright Jason Harrison 20021 Perception of Brightness The physics and psychophysics…"

Similar presentations

Lecture 16 – Lightness Perception

Lecture 16 – Lightness Perception
Physics 1230: Light and Color Ivan I. Smalyukh, Instructor Office: Gamow Tower, F-521 Phone: 303-492-7277 Lectures: Tuesdays.

Physics 1230: Light and Color Ivan I. Smalyukh, Instructor Office: Gamow Tower, F Phone: Lectures: Tuesdays.
Chapter 7: Processing the Image Review structure of the eye Review structure of the retina Review receptive fields –Apply to an image on the retina –Usage.

Chapter 7: Processing the Image Review structure of the eye Review structure of the retina Review receptive fields –Apply to an image on the retina –Usage.
Light and dark adaptation The range of light levels over which we can see Why do we need adaptation? The design problem Role of pupil changes The duplex.

Light and dark adaptation The range of light levels over which we can see Why do we need adaptation? The design problem Role of pupil changes The duplex.
Achromatic and Colored Light CS 288 9/17/1998 Vic.

Achromatic and Colored Light CS 288 9/17/1998 Vic.
776 Computer Vision Jan-Michael Frahm, Enrique Dunn Fall 2014.

776 Computer Vision Jan-Michael Frahm, Enrique Dunn Fall 2014.
Perception Chapter 3 Light is necessary but not sufficient for vision Ganzfeld: a visual field completely lacking in contour, or luminance changes. Prolonged.

Perception Chapter 3 Light is necessary but not sufficient for vision Ganzfeld: a visual field completely lacking in contour, or luminance changes. Prolonged.
1 Computational Vision CSCI 363, Fall 2012 Lecture 33 Color.

1 Computational Vision CSCI 363, Fall 2012 Lecture 33 Color.
Version 0.10 (c) 2007 CELEST VISI  N Star Light, Star Bright, Let’s Explore Light How You Perceive Light How many black dots can you count?

Version 0.10 (c) 2007 CELEST VISI  N Star Light, Star Bright, Let’s Explore Light How You Perceive Light How many black dots can you count?
2002/02/05PSYC202-005, Term 2, Copyright Jason Harrison, 20021 Psychophysics of colour perception Neurophysiology, psychophysics, and magic (or you only.

2002/02/05PSYC , Term 2, Copyright Jason Harrison, Psychophysics of colour perception Neurophysiology, psychophysics, and magic (or you only.
January 8, 2002PSYC202-005, Term 2, Copyright Jason Harrison 20021 Light: Properties and Characteristics Electromagnetic energy you can see.

January 8, 2002PSYC , Term 2, Copyright Jason Harrison Light: Properties and Characteristics Electromagnetic energy you can see.
Sensation Overview How is perception different from sensation? What is psychophysics? What do sense organs do? How does vision work? How does this compare.

Sensation Overview How is perception different from sensation? What is psychophysics? What do sense organs do? How does vision work? How does this compare.
Lecture 30: Light, color, and reflectance CS4670: Computer Vision Noah Snavely.

Lecture 30: Light, color, and reflectance CS4670: Computer Vision Noah Snavely.
Capturing Light… in man and machine 15-463: Computational Photography Alexei Efros, CMU, Fall 2006 Some figures from Steve Seitz, Steve Palmer, Paul Debevec,

Capturing Light… in man and machine : Computational Photography Alexei Efros, CMU, Fall 2006 Some figures from Steve Seitz, Steve Palmer, Paul Debevec,
Brightness and Lightness Brightness: Describe the intensity of the light sources such as sun, candle, Dark, dim, bright, dazzling… Sensation depends on.

Brightness and Lightness Brightness: Describe the intensity of the light sources such as sun, candle, Dark, dim, bright, dazzling… Sensation depends on.
Color, lightness & brightness Lavanya Sharan February 7, 2011.

Color, lightness & brightness Lavanya Sharan February 7, 2011.
Depth of Field depth of fieldConversely, for a given film position, there is a range of distance at which all objects have acceptable images on the film.

Depth of Field depth of fieldConversely, for a given film position, there is a range of distance at which all objects have acceptable images on the film.
Physics 1230: Light and Color Ivan I. Smalyukh, Instructor Office: Gamow Tower, F-521 Phone: 303-492-7277 Lectures: Tuesdays.

Physics 1230: Light and Color Ivan I. Smalyukh, Instructor Office: Gamow Tower, F Phone: Lectures: Tuesdays.
Digital Image Fundamentals Human Vision Lights and Electromagnetic spectrum Image Sensing & Acquisition Sampling & Quantization Basic Relationships b/w.

Digital Image Fundamentals Human Vision Lights and Electromagnetic spectrum Image Sensing & Acquisition Sampling & Quantization Basic Relationships b/w.
COLOR PERCEPTION Physical and Psychological Properties Theories – Trichromatic Theory – Opponent Process Theory Color Deficiencies Color and Lightness.

COLOR PERCEPTION Physical and Psychological Properties Theories – Trichromatic Theory – Opponent Process Theory Color Deficiencies Color and Lightness.

Similar presentations

Ads by Google