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Motion-induced colour mixture

Motion-induced colour mixture. Shin ’ ya Nishida (1), Junji Watanabe (1, 2), Susumu Tachi (2) and Ichiro Kuriki (1) (1) NTT Communication Science Laboratories, Japan (2) The University of Tokyo, Japan. Temporal colour mixture.

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Motion-induced colour mixture

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  1. Motion-induced colour mixture Shin’ya Nishida (1), Junji Watanabe (1, 2), Susumu Tachi (2) and Ichiro Kuriki (1) (1) NTT Communication Science Laboratories, Japan (2) The University of Tokyo, Japan

  2. Temporal colour mixture • Different colours presented closely in time at the same retinal location are perceptually mixed. • Temporal integration improves S/N ratio. • However, temporal integration based on the retinal position is not optimal in our living environment, where colours are often attached to moving objects.

  3. Motion-based colour mixture • Different colours that stimulate different retinal locations, but belong to the same moving object, should be mixed. • Supporting evidence? • Colour mixture induced in moving slits

  4. Time Colour mixture in moving slits • When viewed through rapidly moving slits, stationary stripes of colour appear to have a (tint of) mixed colour of the stripes.

  5. Already on the street in Far East!!

  6. Tracking eye movement? Retinal position Monitor position Time Time

  7. Apparatus & Stimulus • CRS VSG2/5 in Dell Precision 350 • Sony GDM F520 (160Hz, 800 x 600pixels, 1.5min/pixel at 113cm from the monitor) • CRS Video Eyetracker toolbox 2.75° 0.5° 2.75° 20°

  8. Mixed colour bars were presented before and after motion stimulus to mask onset/offset frames Stimulus in space-time Frame duration Exposure duration: 200ms (32 monitor refreshes) Time Colour width Slit width Slit interval

  9. Procedures • 5-scale rating of the degree of colour mixture • Sample stripes were shown during each response period 5: Perfect mixture 4: 3: Partial mixture 2: 1: No mixture

  10. 6.25 12.5 25 50 Stationary 200 Red/Green: Spatiotemporal tuning Frame duration (ms) 5 JW 4 Rating 3 2 1 0 3 6 9 12 15 Colour width (min) Slit width: Colour width x 2 Red: 28 cd/m2 Slit interval: Colour width x 8 Green: 84 cd/m2

  11. 5 6.25 SN 12.5 4 25 50 200 Rating 3 2 1 0 3 6 9 12 15 Colour width (min) Red/Green: Spatiotemporal tuning Frame duration (ms) Slit width: Colour width x 2 Red: 28 cd/m2 Slit interval: Colour width x 8 Green: 84 cd/m2

  12. No eye tracking JW Rating: 5.0 SN Rating: 4.8 Colour width: 6.0min Frame duration: 6.25ms

  13. No change in eye jitter JW SN Error bar:±1SE Rating 5.0 1.0 4.8 1.0

  14. Blue/Yellow: Spatiotemporal tuning Frame duration (ms) JW Slit width: Colour width x 2 Blue: 15 cd/m2 Slit interval: Colour width x 8 Yellow: 112 cd/m2

  15. Blue/Yellow: Spatiotemporal tuning Frame duration (ms) SN Slit width: Colour width x 2 Blue: 15 cd/m2 Slit interval: Colour width x 8 Yellow: 112 cd/m2

  16. Flashing stripes Flashing slits Motion or rapid change? • Stimulus movement induces colour mixture? • Rapid change (high temporal frequency) lowers spatial resolution of the colour system? • As it lowers spatial resolution of the luminance system (Kelly, 1979) Time Moving slits

  17. It’s motion, not rapid change Time Frame duration: 6.25ms JW SN

  18. And more ... • The colour mixture remained to be observed when the two colours in the stripes were equiluminant • An objective test of the perception of mixed colour: Colour matching (Watanabe et al, to be reported at ECVP2004) • Colour matching to motion-induced colour was nearly as accurate as colour matching to physically-mixed colour • Large individual difference • Fixation stability? • Ambiguity in event interpretation?

  19. Direction-selective (DS) Non-DS fine Non-DS coarse Time Possible mechanisms • Direction-selective (DS) mechanisms integrate colours along motion paths • DS mechanisms suppress fine (but not coarse) non-DS mechanisms

  20. Related phenomena • Binocular colour mixture • Motion-induced colour spreading(Cicerone et al., 1995; Chen & Cicerone, 2002) • Colour decomposition in flash-lag(Nijihawan, 1997) • Modulation of chromatic adaptation by target motion (Werner, 2004, VSS) • Spatiotemporal pattern interpolation in multi-slit viewing (Ross, 1977; Burr, 1979; Nishida, in press)

  21. Summary • Colour mixture in moving slits • Neighboring colours are perceptually mixed when they are on the same motion path • Not an eye movement artifact • Only for narrow colour stripes & rapid motion • Induced by motion, not by stimulus change

  22. Conclusion • The visual system integrates colour information across different samples in space and time when they appear to belong to the same moving object. • Colour mixture is not an early-level phenomenon. • Colour processing is tightly linked to motion processing.

  23. Better mixture with narrower slits Frame duration: 6.25ms 2 8 1 4 Time JW SN

  24. Effects of luminance Green > Red > Background G = R > B G = R = B Stimulus Time Perception Space

  25. Motion-induced reduction of colour mixture • Consistent with “direction-selective spatiotemporal integration of colour information” Stimulus Time Perception Space Moving R/G stripes Flicker, but R/G are almost mixed

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