Green-Red Color Contrast Improvement: Feasibility, Effect and Interpretation

Dr. Katalin Tóth

GE Lighting

Global Lighting

Training & Six Sigma Manager

18 September

Same effect with artifictial illumination:

Standard CFL Reveal CFL

Booth testStandard FL 300lux Reveal ® 260 lux

Questions:

1, Which is more colourful2, Where are the contrasts sharper3, Where is the white brighter4, Where is the overall brightness higher

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Answer of 31 observers

Standard Reveal

Individual #1 9 12

Individual #2 16 18

Individual #3 13 21

Individual #4 18 20

Correct answers for Ishihara test

Standard FL 300lux Reveal® 260 lux

Pattern recognition of color deficient individuals

Human Perception

• 2 booths• 3 images• 26 individuals• Luminance set equal in both booths• Compare right lamp with left lamp • Difference was calibrated to the Inc-Reveal pair.

Lamp pairs tested:1 Inca. Std. FL_1 R Ⓡ

2 FL_2 R Ⓡ FL_1 RⓇ

3 FL Std FL_1 R Ⓡ4 FL Standard Inca. Reveal Ⓡ5 FL Standard Inca. Standard6 FL_2 Reveal Ⓡ Inca. Standard7 FL_2 Reveal Ⓡ FL Standard8 FL_2 Reveal Ⓡ Inca. Reveal Ⓡ9 FL_1 Reveal Ⓡ Inca. Reveal Ⓡ

10 Inca Standard Inca. Reveal Ⓡ

Y:Preference scores: right vs. left

-5 0 +5

Left onepreferred

Right onepreferred

Preference of Reveal®-likeperformance confirmed

Individual 95% CI

Pair Mean --------+---------+---------+---------+---

1 Inc Std. FL_1 RⓇ 0.577 (--*---)

2 FL_2 R Ⓡ FL_1 RⓇ-0.000 (---*---)

3 FL Std. FL_1 RⓇ 0.654 (--*---)

4 FL Std. Inc. RⓇ 0.679 (---*---)

5 FL Std. Inc. Std.-0.103 (--*---)

6 FL_2 RⓇ Inc. Std.-0.551 (--*---)

7 FL_2 RⓇ FL Std. -0.526 (---*--)

8 FL_2 RⓇ Inc. RⓇ -0.026 (--*---)

9 FL_1 RⓇ Inc. RⓇ 0.051 (--*---)

10 Inc. Std. Inc. RⓇ 0.808 (--*---)

--------+---------+---------+---------+---

-0.400 0.000 0.400 0.800

Left lamp preferred

Right lamp preferred

NegligibleDifference

Current metrics for quality of light

Standard CFL Reveal®

Incandescent

Improved visual clarity Reveal® FL

Ra 80 78 72

R9 -12 14 23

LPW 65 13 60

Do they reflect perception test results?

Human photoreceptors

Rods:• Achromatic night vision• 1 type

Cones:• Daytime, achromatic and chromatic vision• 3 types

Long-wavelengthsensitive (L) or„red” cone

Middle-wavelength sensitive (M) or „green” cone

Short-wavelengthsensitive (S) or„blue” cone

Why do we have rods and cones

Our vision has to operate over an enormous range of 1012 levels

To cover that range we have two different types of photoreceptors:

• Rods that are optimized for low light levels

• Cones that are optimized for higher light levels

GE inside use only

Rod and cone distribution

• 0.3mm of eccentricity is about 1 deg of visual angle (eccentricity angle) • 120 million rods (absent in the central of fovea (0.3mm fovea centralis), max at 20 deg• At night you have to look away from things to see them in more details• 6-7 million cones (concentrated in the fovea)• During the day you have to look at things directly to see them in detail

GE inside use only

Spectral sensitivity, univariance

• Probability of photon absorption depends upon wavelength• But response is independent of photon wavelength• Change in output could be caused by change in intensity or a change in color• Each photoreceptor is „color blind”, being unable to distinguish between colour and

intensity changes• All the photoreceptor effectively does is to count photons

GE inside use only

Color is encoded by the relative cone outputs

Blue light Red light

Green light

Yellow light White light

Purple light

GE inside use only

Post receptorial color vision

M L M LS

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M-L

CRG

+

Trichomatic stage

Color opponent stage_

S-(M+L)

CBY

Chromaticpathways

GE inside use only

Type of color deficiency

CBY=S-(L+M) CRG= L-M

Neural opponent signals

Spectral response curves of cone cells

Trichomatic stage

Color opponent stage

GE inside use only

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By Katalin Toth/

September 27, 2012

Incandescent Lamps

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Fluorescent lamps

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Incandescent Reveal• filters out yellow (560-620nm)

Fluorescent spectrum: • minimizes addition of yellow

Looks like small change in spectrumSignificant effect in color perception

Reveal Performance

Warm white

Reveal®

TriphosTest#4

Reveal®

Standard

Emission spectra

GE inside use only

RG neural opponent signaladapted tostandard FL

GE inside use only

RG neural opponent signal adapted toReveal® FLResulting increased green-red contrast, gamut and better color rendering for red color

Protanomal’s RG neural opponent signal adapted to Reveal® FL

®

GE inside use only

21 /

By Katalin Toth/

September 27, 2012

CIE color-matching functions

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SPD of Inca.

SPD of Reveal Incan.

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By Katalin Toth/

September 27, 2012

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SPD of Standard CFL

SPD of Reveal CFL

CIE color-matching functions

546 Hg line

23 /

By Katalin Toth/

September 27, 2012

Color contrast improvement summary:

• Make colour more vivid: increased chroma

• Improve green-red contrast

• Good for person with certain type colour-deficiency

• Increase perceived illumination level

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By Katalin Toth/

September 27, 2012

Thank you for your attention!