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High Color-Fidelity Imaging System Using B/W Digital Camera and

Rotary Color Filters

Fuji Photo Film Hitoshi UrabeMitsubishi Electric Hiroaki Sugiura

NoteThis research was organized in part by the New Energy and Industrial Technology Development Organization, Japan(NEDO).

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Part 1: To develop NEDO-DSC to aquire a high-resolution

colorimetric image to reproduce an actual scene.

Part 2: Its applications

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Scene

Capturing

Part 1 : Backgrounduse case : RAW-DSC for professional user

Appearance conv.

Mapping to device

Monitor Print

XYZ X’Y’Z’

RGBorCMYColorimetric color reproduction

4Color Filter B/W DSC

Capturing deviceHigh accurate and high fidelity color capturing system

B/W DSC with rotary color filters

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Transmittance spectra of the color filters

0

0.2

0.4

0.6

0.8

1

380 480 580 680 780wavelength(nm)

trans

mitt

amce

Filter1

Filter2

Filter3

6

0

0.25

0.5

0.75

1

380 480 580 680 780w avelength (nm)

sens

itivity

)(λx

)(λy

)(λz)(λx′

)(λy

)(λz′

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Evaluation of the spectral sensitivities

Neugebauer’s quality factor

Measure of Goodness by Vora and Trussell

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1

2 saqi

i∑=

=

33

1∑=

≡i

iqν

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Q-factor andν

DSC R G B

NEDO-DSC 0.999 0.992 0.983 0.991

DSC（Company A） 0.776 0.996 0.874 0.882

DSC（Company B） 0.813 0.941 0.848 0.867

ν

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Color registration

Color Filter

Optical Axis

Actual ray of light

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Registration check

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Registration error

Type Filter X(pixel) Y(pixel) Rotation(deg.)

ARB

0.025514-0.024398

0.0994840.014183

0.00100.0005

ARB

-0.033403-0.074217

0.038653-0.020859

-0.0001-0.0002

BRB

0.012775-0.067492

0.029657-0.016036

-0.0005-0.0005

BRB

-0.032086-0.087687

0.0118660.055662

-0.0002-0.0001

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Data processing procedure

RAW images

Honeycomb interpolation

Interpolated image

XYZ conv.

Calibration data

XYZ image

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Calibration method

Scene :Macbeth&NCS chart& white plate

Spectroradiometer

B/W DSC with R-CF

Chart:Plate:

nnn BGR ,,www BGR ,,

Tristimulus values

Chart:Plate:

nnn ZYX ,,www BGR ,,

Image data

1

1

1

1

1

1

1

''''''G''' −

⎟⎟⎟

⎠

⎞

⎜⎜⎜

⎝

⎛

⎟⎟⎟

⎠

⎞

⎜⎜⎜

⎝

⎛=

wn

wn

wn

wn

wn

wn

BBBGGRRR

ZZZYYYXXX

A･･･

･･･

･･･

･･･

･･･

･･･

⎪⎩

⎪⎨

⎧

−−=−−=−−=

)/()(')/()(')/()('

γγββαα

wnn

wnn

wnn

BBBGGGRRR

3×3 MTX:Correction terms:

Aγβα ,,

Calibration data

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Spectra of the illuminants

0

2

4

6

8

10

12

380 480 580 680 780w avelength (nm)

radi

ant e

nerg

y (Y

=100

)1: FL40SSW/37(TOSHIBA)2: XC-500AF(SERIC)3: PRF500WD(IWASAKI)

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Colorimetric accuracy of NEDO-DSC

Illuminant

1(FL40SSW/37) 1.77 0.38 6.27

2(XC-500AF) 1.86 0.54 6.25

3(PRF500WD) 2.08 0.72 7.44

EΔ gEΔ maxEΔ

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Comparison between NEDO-DSC and Spectro-radiometer

-60

-40

-20

0

20

40

60

80

-60 -40 -20 0 20 40 60

a*

b* PR650

NEDO-DSC

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Comparison between NEDO-DSC and commercially available DSC(S2Pro)

-60

-40

-20

0

20

40

60

80

-60 -40 -20 0 20 40 60

a*

b* NEDO-DSC

S2Pro

18NEDO-DSCDSC(S2Pro)

sRGB image appearance

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Conclusion

NEDO-DSC has good results as follows.(1)Average delta-E = 1.86

to MacBeth 24 and NCS 40 colours andAverage delta-E = 0.54 to MacBeth 6 grays under XC-500AF（SERIC） illuminant.

(2)Much better than commercially available DSC(S2Pro) in terms of Colorimetric reproduction.

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Part 2 : Its applications.Actual scene-referred colour space

using NEDO-DSC

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Color gamut of actual scenesProceduresScene : 5 scenes were captured using NEDO-DSC.

Each scene has extremely saturated objects including plastics, textiles and so on.

Calibration targets : Macbeth(24), NCS(40) and W-plate

Calculation ： Most saturated colors of each scene were calculated in L* in every deltaL*=10 and

Hue in every 10 degree.

Then, outer most boundary(Maximum C* of 5 scenes) were calculated and plotted in next slides.

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Five scenes

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Actual scene-referred color gamut（D65）

：OptimalColor：Target5

：AdobeRGB

Lab color space (L*= 20)

-160

-120

-80

-40

0

40

80

120

160

-200 -160 -120 -80 -40 0 40 80 120 160

a*

b*

O ptim alC olor

Target5

AdobeRG B

Lab color space (L*= 50)

-160

-120

-80

-40

0

40

80

120

160

-200 -160 -120 -80 -40 0 40 80 120 160

a*

b*

O ptim alC olor

Target5

AdobeRG B

Lab color space (L*= 80)

-160

-120

-80

-40

0

40

80

120

160

-200 -160 -120 -80 -40 0 40 80 120 160

a*

b*

O ptim alC olor

Target5

AdobeRG B

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Actual scene-referred color gamut（D65）

：OptimalColor：Target5

：AdobeRGB

C -R (190°～40°)

0

10

20

30

40

50

60

70

80

90

100

-200 -150 -100 -50 0 50 100 150 200

C *

L*

O ptim alC olor

Target5

AdobeRG B

M -G (330°～150°)

0

10

20

30

40

50

60

70

80

90

100

-200 -150 -100 -50 0 50 100 150 200

C *

L*

O ptim alC olor

Target5

AdobeRG B

B-Y (310°～100°)

0

10

20

30

40

50

60

70

80

90

100

-200 -150 -100 -50 0 50 100 150 200

C *

L*

O ptim alC olor

Target5

AdobeRG B

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Part 2 : Its applications.In case of transmissive and

fluorescent objects

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Eight semi-ransmissive scenes

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0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

380 420 460 500 540 580 620 660 700 740 780

nm

inten

sity

ST_No13ST_No15ST_No16WhitePlate

Spectral distribution of semi-transmissive objects

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Part 2 : Its applications.Actual scene-referred colour space

using NEDO-DSC

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Spectral distribution of UV illuminant

0

50000

100000

150000

200000

300 400 500 600 700 800

nm

Relat

ive In

tens

ity

With UVWithout UV

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Four fluorescent scenes

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0.0

0.5

1.0

1.5

2.0

2.5

380 420 460 500 540 580 620 660 700 740 780

nm

inten

sity

No14No15WhitePlate

Spectral distribution of fluorescent objects

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Future Challenges

To define actual scene-referred colour gamut

To develop estimating method of colorimetric characteristics of high-end RAW-DSCs

AcknowledgementThis research was organized in part by the New Energy and Industrial Technology Development Organization, Japan(NEDO).

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Thank you for your attention.