Leds experiments in paris 1 colour rendering 2 kruithof s rule
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LEDs experiments in Paris 1. Colour rendering 2. Kruithof’s rule. F. Viénot, E. Mahler, A. Rambaud, M.-L. Durand, C. Boust, J.-J. Ezrati, CRCC, Muséum national d’histoire naturelle CIE, TC1-69, Stockholm, June 2008. Colour rendering - Illumination. WWARGB. WR. RGBA. RGB. LED clusters

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LEDs experiments in Paris 1. Colour rendering 2. Kruithof’s rule

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Leds experiments in paris 1 colour rendering 2 kruithof s rule

LEDs experiments in Paris1. Colour rendering2. Kruithof’s rule

F. Viénot, E. Mahler, A. Rambaud, M.-L. Durand, C. Boust, J.-J. Ezrati,

CRCC, Muséum national d’histoire naturelle

CIE, TC1-69, Stockholm, June 2008


Colour rendering illumination

Colour rendering - Illumination

WWARGB

WR

RGBA

RGB

  • LED clusters

    RGB LEDs “RGB”

    RGB+Amber LEDs “RGBA”

    two-phosphor cold white LED + Red LED “WR”

    two-phosphor cold white LED + two-phosphor warm white LED + Amber + RGB LEDs “WWARGB”

  • Control light : Solux filtered tungsten-halogen lamp

Solux


Colour rendering discrimination

Colour rendering - Discrimination

  • Distribution of errors

RGB

Solux


Colour rendering appearance

Colour rendering - Appearance

Distribution of colourfulness ratings

Distribution of hues

Solux WWRGBA RGB

Red ->

<- Red

RGB

Yellow ->

<- Yellow

Colourfulness rating

<- Green

Green ->

Blue ->

<- Blue

Red ->

<- Red


Colour rendering conclusion

Colour rendering - Conclusion

  • Colour rendering

    • either Colour fidelity, colour discrimination

    • or Colourfulness enhancement

  • Different tasks and different visual coding

  • Results of thiese experiments can be predicted from CIELAB or CIECAM02

  • Agreement with

    Rea Mark S., Freyssinier-Nova Jean P., 2008, Color Rendering: A Tale of Two Metrics, COLOR research and application, 33: 192-202.


Kruithof s rule background

Kruithof’s rule - Background

Kruithof, A. A.: Tubular Luminescence Lamps for General Illumination, Philips Technical Review 6, pp. 65-96 (1941).

Kruithof has examined the illuminance limits between which users find the illumination “pleasant”.

Kruithof’s diagram (Fig. 10) shows the accepted combination of illuminance and colour temperature.

The author states that, globally, a low and high illumination should correspond to a low and high colour temperature, respectively (my translation).

Illuminance (log scale)

Correlated colour temperature


Re examination of kruithof s rule objectives

Re-examination of Kruithof’s ruleObjectives

  • Since LED illumination is very flexible in terms of luminous intensity and colour temperature, we have planned an experiment to re-examine this rule, questioning the interpretation and the physiological basis of the “pleasantness” sensation.

  • Collaborators

    • Marie-Lucie Durand, Paris-Orsay University

    • Elodie Mahler, SNCF, France


Re examination of kruithof s rule methods

Re-examination of Kruithof’s rule Methods

  • Light booth equipped with LEDs (cool white, warm white, orange, amber, green, cyan, blue)

  • Illuminance : 150, 300 and 600 lx

  • Correlated colour temperature : 2700, 4000, 6500 K

  • Optimised CRI > 86


Re examination of kruithof s rule tasks

Re-examination of Kruithof’s rule Tasks

  • Three type of tasks

    • Performance (acuity, contrast threshold, reading)

    • Color perception (hue appearance, colour preference, cognitive colours)

    • Subjective feeling (pleasantness, mood, …)

  • Methods (depending upon the task)

    • Scaling, ranking, thresholds, category scaling, semantic analysis, ANOVA

  • 30 young observers


Re examination of kruithof s rule performance

Re-examination of Kruithof’s rule Performance

  • Example of low-contrast acuity

low-contrast acuity (log)

Illuminations

Y in cd.m-2


Re examination of kruithof s rule colour appearance

Re-examination of Kruithof’s rule Colour appearance

  • Example of location of binary hues


Re examination of kruithof s rule sensation scale

Re-examination of Kruithof’s rule Sensation scale

  • Example of lightness sensation

Perceived lightness scale

Illuminations

Y in cd.m-2


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