Computer Laboratory

Projects

Omni-CSF: A Comprehensive Spatio-Chromatic Contrast Sensitivity Function for High-Dynamic Range

Sophie Wuerger, Maliha Ashraf, Minjung Kim, Jasna Martinovic, María Pérez-Ortiz, Rafał K. Mantiuk


The omni-CSF describes contrast sensitivity across a wide range of stimulus parameters. It spans luminance levels from the dimly lit sky of a motorway at night (0.002 cd/m2) to the bright sky on a sunny day (10000 cd/m2), which makes the omni-CSF appropriate for predicting visibility on high-dynamic range (HDR) displays.

Table of Contents

  1. Introduction
  2. Omni-CSF
    • Datasets
    • Publications
  3. Applications of the Omni-CSF
    • Publications
  4. CSF and Ageing Vision
    • Publications
  5. Contact

Introduction

Contrast thresholds describe the minimum difference in luminance or chromaticity that a human observer can detect. Contrast thresholds depend on a number of viewing and stimulus parameters, and the dependence of contrast thresholds to such parameters is described by contrast sensitivity functions (CSFs). Having an accurate CSF is important for image and video coding applications, as contrast thresholds provide a limit to the amount of colour reproduction error that is noticeable to a human observer.

The purpose of this project was to develop a comprehensive, omni-directional CSF (omni-CSF) that spans a large range of stimulus parameters:

  • Spatial frequencies in 0.125 cpd to 32 cpd (human upper limit is approximately 60 cpd)
  • Mean luminance in mesopic levels (0.002 cd/m2) to high photopic levels (10000 cd/m2)
  • Any colour modulation direction
  • Any background colour
  • Any size

To achieve that,

  • We acquired six datasets of contrast sensitivity measurements and standardised them to LMS colour space, assuming CIE 2006 cone fundamentals
  • The omni-CSF was fitted to all datasets. This model describes the contrast sensitivity of a healthy, average adult between age 20 and 40.

Using the omni-CSF,

  • We developed a model for predicting the visibility of banding artefacts in HDR images.
  • We developed color threshold functions (CTFs), which are contrast detection thresholds expressed in well-known, application-oriented colour spaces, such as sRGB and CIE L*a*b*.

We also measured contrast sensitivities of older observers (age 65 and above) and developed a CSF that accounts for age-related changes in vision.

Omni-CSF

Datasets

Dataset Background Color Background Luminance Colour Modulation Direction Spatial Frequency Stimulus Size Gabor Type Figures
Wuerger et al. (2002).
Proceedings of SPIE, Vol. 4662, Human Vision and Electronic Imaging VII.
Custom grey 40 cd/m² Black ↔ White
Green ↔ Red
Yellow-green ↔ Violet
Greenish ↔ Pink
Yellow ↔ Blue
Dark green ↔ Light pink
Dark yellow ↔ Light blue
1 - 32 cpd 0.5° Fixed size [omni-CSF fit]
Mantiuk et al. (2011).
ACM Transactions on Graphics.
D65 0.0002 - 150 cd/m² Black ↔ White 0.125 - 32 cpd 0.15°, 0.5°, 1.5° Fixed size [omni-CSF fit]
Kim et al. (2013).
Proceedings of SPIE, Vol. 8651, Human Vision and Electronic Imaging XVIII.
D65 0.02 - 200 cd/m² Green ↔ Red
Yellow-green ↔ Violet
Dark green ↔ Light pink
Dark Yellow ↔ Light blue
0.25 - 16 cpd 1.5°, 3° Fixed size [omni-CSF fit]
Xu et al. (2020).
Inaugural London Imaging Meeting.
Grey, red, green, yellow, blue 8.2 - 70 cd/m² 9 directions on the isoluminant plane 0.06 - 3.84 cpd 9.3° Fixed size [omni-CSF fit]
Wuerger et al. (2020).
Journal of Vision.
[cite] [data] [code]
D65 0.02 - 10000 cd/m² Black ↔ White
Green ↔ Red
Yellow green ↔ Violet
0.125 - 6 cpd 0.0417-4° Fixed cycles [stimuli]
[data figure 1]
[data figure 2][omni-CSF fit]
Mantiuk et al. (in preparation). Grey, red, green, yellow, blue

Publications

Journal Articles and Conference Proceedings

  • Mantiuk, R. K., Kim, M., Ashraf, M., Xu, Q., Luo, M. R., Martinovic, J. and Wuerger, S. M. (2020). Practical color contrast sensitivity functions for luminance levels up to 10000 cd/m2. 28th Color and Imaging Conference. 4-19 November 2020.
  • [download] Kim, Ashraf, Perez-Ortiz, Martinovic, Wuerger and Mantiuk. (2020). Contrast sensitivity functions for HDR displays. Inaugural London Imaging Meeting. 30 September 2020-1 October 2020.
  • [download] Wuerger, Ashraf, Kim, Martinovic, Perez-Ortiz and Mantiuk. (2020). Spatio-chromatic contrast sensitivity under mesopic and photopic light levels. Journal of Vision. 20(4):23. doi:10.1167/jov.20.4.23.
    [data] [code]
  • [download] Ashraf, M., Wuerger, S. M., Mantiuk, R. K., and Martinovic, J. (2019). Luminance and chromatic contrast sensitivity at high light levels. I-Perception. 10, 5. doi:10.1177/2041669519854233.

Conference Talks without Proceedings

Conference Posters without Proceedings

  • [download] Ashraf, M., Wuerger, S., Mantiuk, R. K., Kim, M., and Martinovic, J. (2019). Luminance and chromatic contrast sensitivity for extended range of light levels. Poster Presentation at Liverpool Neuroscience Day (LND). 14 June 2019, Liverpool, UK.
  • [download] Wuerger, Mantiuk, Perez-Ortiz and Martinovic. (2019). Luminance and chromatic contrast sensitivity at high light levels. Journal of Vision. 19(10):70b. doi:10.1167/19.10.70b.
  • [download] Ashraf, M., Wuerger, S. M., Mantiuk, R. K., Kim, M., and Martinovic, J. (2019). Luminance-dependent spatio-chromatic sensitivity: from detection to appearance. Poster Presentation at Leeds Colour Conference. 29-30 July 2019, Leeds, UK.
  • [download] Perez-Ortiz, Martinovic, Mantiuk, and Wuerger. (2019). Luminance and Chromatic Contrast Sensitivity at High Light Levels. Perception.

Applications of the Omni-CSF

Publications

Conference Proceedings

  • [download] Kim, M., Azimi, M. and Mantiuk, R. K. (2020). Perceptually motivated model for predicting banding artefacts in high-dynamic range images. 28th Color and Imaging Conference. 4-19 November 2020.
  • [in review] Kim, M., Azimi, M. and Mantiuk, R. K. (under review). Color Threshold Functions: Application of Contrast Sensitivity Functions in Standard and High Dynamic Range Color Spaces.

CSF and Ageing Vision

Publications

Conference Proceedings

  • Ashraf, M., Wuerger, S., Kim, M., Martinovic, J. and Mantiuk, R. K. (2020). Spatio-chromatic contrast sensitivity across the lifespan: interactions between age and light level in high dynamic range. 28th Color and Imaging Conference. 4-19 November 2020.

Conference Posters without Proceedings

  • [download] Ashraf, M., Wuerger, S. M., Mantiuk, R. K., Kim, M., Saunderson, H., and Martinovic, J. (2019). Age-related changes in spatio-chromatic contrast sensitivity at mesopic and photopic light levels. Poster Presentation at Women in Vision UK Meeting. 13 December 2019, Belfast, UK.

Contact

Please contact Rafał Mantiuk or Sophie Wuerger.