I’ve never metamer I didn’t like
John Seymour John the Math Guy, LLC Adjunct Prof., Clemson Part 1 What is Metamerism? What is metamerism?
§My wife’s favorite color word §Two samples matching under one illuminant, but not another What is metamerism?
The shadows do not tell the full story.
The eye does not see each wavelength of the spectrum. What is metamerism?
The shadows do not tell the full All the eye sees is a story. projection of that spectrum onto the The eye does not spectral response see each our three cones. wavelength of the spectrum. Actual metamers Not a metameric pair
Indoor Outdoor lighting lighting Metameric pairs in industry Part 2 The metameric database Metameric database
§Target colors from Pantone book §Searched § Flexo, CMYK and EG § Indigo 7900, CMYK and EG § GOE §Adjusted to make perfect metameric match §~3,600 metameric pairs The following slides contain mathematical material and graphs which may trigger mathaphobic responses in some viewers. Metamers under D50 with 2o observer
Flexo EG version
Pantone version Metamers under D50 with 2o observer
Flexo EG version
Pantone version
L*a*b* 56, 27, 47 Metamers under D50 with 2o observer
Flexo EG version
Pantone version
L*a*b* 61, 21, 0 Metamers under D50 with 2o observer
Pantone version
Flexo EG version L*a*b* 54, -66, 28 Metameric sextuplets
Pantone Flexo CMYK Flexo EG GOE Indigo 7900 CMYK Indigo 7900 EG 6 ways to make a dark greenish brown
Pantone Flexo CMYK Flexo EG GOE Indigo 7900 CMYK Indigo 7900 EG Part 3 Metamerism of spot color replacement Two different standards
§Daylight 50 illuminant / 2o observer – printing §Daylight 65 illuminant / 10o observer – everywhere else Revisting one metameric pair
Flexo EG version
Pantone version Pantone version Same spectra with D50 and D65
D65
D50
Emphasized by D50
Emphasized by D65 Comparing D50 and D65
§Very similar shape §D50 emphasizes what happens above 580 nm §D65 emphasizes what happens below 540 nm §Colors that match under D50 may not match under D65 Metameric sextuplets
Pantone Flexo CMYK Flexo EG GOE Indigo 7900 CMYK Indigo 7900 EG Color difference under D65/10
Process PMS 147C
Flexo CMYK 0.09 DE00 Flexo EG GOE Indigo 7900 CMYK Indigo 7900 EG Metameric sextuplets
Pantone Flexo CMYK Flexo EG GOE Indigo 7900 CMYK Indigo 7900 EG Color difference under D65/10
Process PMS 147C
Flexo CMYK 0.09 DE00 Flexo EG GOE Indigo 7900 CMYK
Indigo 7900 EG 0.16 DE00 Metameric sextuplets
Pantone Flexo CMYK Flexo EG GOE Indigo 7900 CMYK Indigo 7900 EG Color difference under D65/10
Process PMS 147C
Flexo CMYK 0.09 DE00 Flexo EG
GOE 1.44 DE00 Indigo 7900 CMYK
Indigo 7900 EG 0.16 DE00 Color difference under D65/10
Process PMS 147C
Flexo CMYK 0.09 DE00
Flexo EG 0.59 DE00
GOE 1.44 DE00
Indigo 7900 CMYK 0.50 DE00
Indigo 7900 EG 0.16 DE00 Identical sextuplets
Pantone Flexo CMYK Flexo EG GOE Indigo 7900 CMYK Indigo 7900 EG Color difference under D65/10
Process PMS 147C PMS 5787C
Flexo CMYK 0.09 DE00 0.05 DE00
Flexo EG 0.59 DE00 0.06 DE00
GOE 1.44 DE00 0.05 DE00
Indigo 7900 CMYK 0.50 DE00 0.10 DE00
Indigo 7900 EG 0.16 DE00 0.06 DE00 Another set of sextuplets
Pantone Flexo CMYK Flexo EG GOE Indigo 7900 CMYK Indigo 7900 EG Color difference under D65/10
Process PMS 147C PMS 5787C PMS 7411C
Flexo CMYK 0.09 DE00 0.05 DE00 0.39 DE00
Flexo EG 0.59 DE00 0.06 DE00 1.12 DE00
GOE 1.44 DE00 0.05 DE00 2.10 DE00
Indigo 7900 CMYK 0.50 DE00 0.10 DE00 0.94 DE00
Indigo 7900 EG 0.16 DE00 0.06 DE00 1.32 DE00 Metameric database
§We looked at 15 matches to Pantone colors §I have 3,589 more §Should we look at them all? Distribution of color diff under D65/10 Proportion in tolerance Proportion
DE00 Distribution of color diff under D65/10
th 99 ptile 4.37 DE00 th 90 ptile 2.18 DE00
Median 0.72 DE00 Distribution of color diff under D65/10
88.6% of the time in tolerance
11.4% of the time not in tolerance If we set a tolerance of 2.0 DE00 Bottom line
§If you replace a traditional spot color with another set of pigments, §And you get a perfect match under D50/2, §Then you have an 8 in 9 chance of having an acceptable match under D65/10. Is this a problem?
§1 in 9 will be out of §When will the original and tolerance the replaced version ever §The difference could be be side-by-side?
up to 5.8 DE00 §And under D65 illuminant? Metamerism of spot color replacement
§Perfect D50/2 metameric replacements of spot colors can be a poor match under D65/10. §This doesn’t mean EG spot color replacement is a bad idea! §Setting expectations. Part 4 Other illuminants Assortment of CIE illuminants
CIE name Nickname Color temp Color rendering D65/2 Ave day / small 6500K 100 D50/10 Noon sky / large 5000K 100 D65/10 Ave day / large 6500K 100 A/2 Incandescent 2856K 100 F2/2 CWF 4140K 62 F4/2 WWF 3000K 53 F11/2 TL84 4100K 86 F12/2 TL830 3000K 86
Nickname, color temp, and color rendering from Various Light Sources and Their Use In Color Matching, by gti F2 and F4 illuminants
WWF
CWF TL84
§Three-phosphor fluorescent tube §Common store lighting in Europe §CIE F11 based on this TL830
§Three-phosphor fluorescent tube §Common store lighting in USA §CIE F12 based on this F11 and F12
F12
F11 Metamerism for common lighting
D65/2 D50/10 D65/10 A/2 F2/2 F4/2 F11/2 F12/2 Metamerism for common lighting
D65/2 D50/10 D65/10 A/2 F2/2 F4/2 F11/2 F12/2 Metamerism under three conditions
§Switching from D50 to D65 has an effect §Switching from 2o observer to 10o has an effect §The effects combine Metamerism for common lighting
D65/2 D50/10 D65/10 A/2 F2/2 F4/2 F11/2 F12/2 Three similar illuminants
§Similar in degree of metamerism § D65/10 – average daylight, large area § A/2 – Incandescent, small area § F2/2 – Cool white fluorescent, small area §In general, not in specific cases Metamerism for common lighting
D65/2 D50/10 D65/10 A/2 F2/2 F4/2 F11/2 F12/2 Three similar illuminants
§Problem children in terms of metamerism § F4 – Warm white fluorescent § F11 – similar to TL84 § F12 – similar to TL830 Three problem children
§Some common illuminants can show large metamerism §D65/10 is not necessarily a good test of metamerism Metamerism under CIE illuminants
CIE name Nickname Color temp Color rendering Median DE00 % < 2 DE00
D65/2 Ave day / small 6500K 100 0.27 DE00 0.5%
D50/10 Noon sky / large 5000K 100 0.44 DE00 3.0%
D65/10 Ave day / large 6500K 100 0.72 DE00 11.4%
A/2 Incandescent 2856K 100 0.70 DE00 15.0%
F2/2 CWF 4140K 62 0.84 DE00 16.2%
F4/2 WWF 3000K 53 1.39 DE00 34.9%
F11/2 TL84 4100K 86 1.28 DE00 24.7%
F12/2 TL830 3000K 86 1.34 DE00 28.5% Part 5 White LEDs What about white LEDs?????
7400K
6000K
4550K RGB
Warm white 2800K RGB LED White Cool white Flashlight Metamerism for white LEDs
Warm white RGB LED White Cool white Flashlight D65/10 Metamerism under white LEDs
CIE name Nickname Color temp Color rendering Median DE00 % < 2 DE00
Warm white 2800K 83 0.78 DE00 14.7%
RGB LED 3650K 93 0.50 DE00 2.7%
White 4550K 81 0.53 DE00 0.2%
Cool white 6000K 80 0.65 DE00 4.0%
Flashlight 7400K 78 0.71 DE00 6.7% White LEDs – metamerism problem?
§White LEDs show similar or less metamerism to D65/10 §White LED lighting is not such a big problem, metamerically speaking Part 6 Viewing booth metamerism Motivation
§I found three types of viewing booths in the field §None of them are true D50 Three types of viewing booths
F3.1 F8 Multiple LED D50 Motivation
§I found three types of viewing booths in the field §None of them are true D50 §All are approximations of D50 §Potential for viewing booth metamerism §Those spikes look scary! Viewing booth metamerism
Errors due to booths
Errors due to D65/10
Booth type 1 Booth type 2 LED booth F3.14 F8 D65/10 Viewing booth metamerism?
§Not nearly as large as D65/10 metamerism §Let’s worry about something else Viewing booth metamerism
Booth type 1 Note Booth type 2 change in LED booth scale! F3.14 F8 D65/10 Overall summary
§Large metameric database created §Spot color replacement – 1 in 9 chance of being out of tolerance on D65/10 §WWF, TL83 and TL830 are common FLs §WWF, TL83 and TL830 are bigger problems §White LEDs are not a big problem §Viewing booth metamerism is minimal Thank you for not snoring too loudly! John Seymour [email protected] Clickhttp://johnthemathguy.blogspot.com/ to edit Master subtitle style
John the Math Guy