pigmented colorants: dependence on media and time - Cornell ...

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Table 6.1: Color conversions from the spectral reflectances of the samples of Lapis Lazuli in different binding media, dry after one day. X Y Z H V C L ∗ a ∗ b ∗ acrylic 10.04 10.50 28.19 2.54PB 3.76 7.06 38.73 0.67 -33.74 casein 21.35 24.01 45.42 8.86B 5.44 5.78 56.10 -6.60 -25.85 distemper 13.28 14.43 35.06 1.29PB 4.35 7.12 44.85 -2.62 -32.83 encaustic 7.75 8.06 17.09 2.54PB 3.32 4.18 34.12 0.96 -22.00 gouache 9.03 9.46 26.48 2.43PB 3.58 7.13 36.85 0.53 -34.33 oil 12.40 13.26 37.67 1.97PB 4.19 8.48 43.15 -1.18 -39.09 tempera 7.53 7.89 17.38 2.25PB 3.29 4.47 33.75 0.46 -23.24 watercolor 7.49 7.58 19.51 3.60PB 3.22 5.66 33.09 2.93 -28.66 pany who currently produces the Munsell Book of Color [Mun]), which computes many conversions from XY Z values (including Munsell HV C, L ∗ a ∗ b ∗ , RGB and CMY K) [Gre06]. Different color system values computed from the eight differing binding media reflectance spectra in Figure 6.1 are shown in Table 6.1. We now have a discrete way of evaluating the magnitude of the perceptual differences ∆E between colors. Using the converted L ∗ a ∗ b ∗ colors, one can estimate the perceived difference between colors via the magnitude of its distance from another color in space. Table 6.2 describes the distance between every L ∗ a ∗ b ∗ color in Table 6.1. From this data, we can infer how Lapis Lazuli differs perceptually in the eight binding media. Small values of ∆E indicate that a pair of colors are very similar to each other, while large values show that the two colors are very different. One can see that paint samples of Lapis lazuli in encaustic and tempera are 171 the most similar colors after one day of drying. While the two samples are very
172 Table 6.2: Perceptual differences between binding media. Table of perceptual differences ∆E between colors using the L ∗ a ∗ b ∗ color space. The colors are converted from samples of Lapis Lazuli in different binding media, dry after one day. casein 20.416 acrylic casein distemper encaustic gouache oil tempera distemper 7.008 13.825 encaustic 12.616 23.561 15.660 gouache 1.975 22.211 8.728 12.636 oil 7.182 19.297 6.645 19.447 8.079 tempera 11.623 23.583 14.989 1.387 11.515 18.501 watercolor 7.920 25.064 13.656 7.021 7.214 15.063 5.993 similar (as the measure ∆E is small), they are still many times the average human’s threshold for detectable differences. Also, by examining the data set from any of the color spaces (XY Z, HV C, orL ∗ a ∗ b ∗ ), one can readily see the close relation between the two colors–the coordinates of both colors in each space are very similar. Therefore, it is safe to presume that the two samples have comparable spectral reflectance curves. Examining the data from Figure 6.1, one can see that the encaustic and tempera samples are nearly collinear. In contrast, the colors that differ the most for Lapis Lazuli are the media casein and watercolor. Much of this difference is due to the drastically different values of luminance for the two samples. Using any of the color systems (XY Z, HV C, L ∗ a ∗ b ∗ ), one notices in each that casein has the highest luminance (Y , V , or L ∗ , respectively) in each scale, while watercolor has the lowest. In the spectral reflectance plots, this is depicted as casein reflecting the most light over the visible spectrum while watercolor reflects much less light. A comparison of
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PIGMENTED COLORANTS: DEPENDENCE ON
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ABSTRACT We present a physically ba
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Acknowledgements This work would no
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Table of Contents 1 Introduction 1
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List of Tables 2.1 Average pigment
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3.15 Photoreceptor absorption .....
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B.15 Variation of spectral reflecta
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corrode the surfaces of materials.
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Figure 1.1: Detail of the Azor-Sado
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However, since mural artwork is typ
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at a very high quality (albeit limi
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heterogeneous sum of very different
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which linseed oil derives (the most
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oration of a rigidly painted layer
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ing will hit the ground and reflect
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tion of paint tubes in 1841 and the
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Figure 2.8: Natural pigments of ant
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ecome more common recently. The Ame
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A V = O(r2 ) O(r3 ) = 1 O(r) 24 (2.
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Table 2.2: Pigment specific gravity
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provide the underlying color to a p
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though the speed of light in air is
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In general, when light travels from
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materials while lit from behind. Li
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Table 2.4: Index of refraction η f
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to completely congeal. Hence, these
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ond together to form proteins. Exam
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to its original state by any means.
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While it has been used since the 19
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organic binder found in more conven
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3.1.1 Visible Light Spectrum Light
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Figure 3.2: Hue, brightness and sat
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measures how much light is reflecte
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Figure 3.6: Additive color mixing o
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Figure 3.9: The physical amount of
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The vascular tunic lies on the wall
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Figure 3.11: Cross section of the r
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Not all areas have the same sensiti
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identify and distinguish between va
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that range between zero and full in
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spectrum. This insures that the res
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Figure 3.19: Graphical representati
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X x = (X + Y + Z) Y y = (X + Y + Z)
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color into the appropriate RGB colo
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components in the image (the smalle
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haviors of subtractive mixing and i
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of perceptually equal sizes. Unfort
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enabling one to transform between t
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andwidth as converted signals are s
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Figure 3.28: Retinal ganglion recep
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example shown in Figure 3.28. Under
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Figure 3.31: The work of Josef Albe
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sensations for each trial and picke
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Chapter 4 Previous Work There is no
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different location. Subsurface scat
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describes the scattering and absorp
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only accounts for a small percentag
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σ ′ t = σa + σ ′ s and α
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104 Figure 4.4: A model of an alaba
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effects or are too computationally
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108 Figure 4.6: Results using Kubel
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specifying pigments works adequatel
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color representation, it is not fea
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time. A metallic surface patina is
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the system consisted of wetness and
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or darkening enables the museum per
Page 133 and 134: in front of a displayed work. Felle
Page 135 and 136: light exposure. This effect is espe
Page 137 and 138: over time. Perceptually, these hues
Page 139 and 140: The rate of change of the concentra
Page 141 and 142: over white grounds) suffer the grea
Page 143 and 144: protects the deeper remaining color
Page 145 and 146: light source. This method is used w
Page 147 and 148: chemical smog and have been identif
Page 149 and 150: Chapter 5 Preparation & Measurement
Page 151 and 152: tending transparent pigments used i
Page 153 and 154: 140 Figure 5.1: Spectral reflectanc
Page 155 and 156: the requirements of the work at han
Page 157 and 158: 144 Figure 5.2: Left: Magnified vie
Page 159 and 160: Table 5.2: Relevant data regarding
Page 161 and 162: historically one of the best grades
Page 163 and 164: created far too strong of a binder,
Page 165 and 166: too brittle and cracking. While wor
Page 167 and 168: 154 Figure 5.4: Reflectance values
Page 169 and 170: 5.1.5 Painting After the layers of
Page 171 and 172: The gray card reflected 18% of the
Page 173 and 174: 160 Figure 5.8: The optical setup f
Page 175 and 176: Note that harmonics reflect at the
Page 177 and 178: Note that the calibration factors f
Page 179 and 180: Chapter 6 Experimental Results 6.1
Page 181 and 182: 168 Figure 6.1: Lapis Lazuli in dif
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Page 187 and 188: 174 Figure 6.3: Munsell plots of La
Page 189 and 190: and j has a saturation of red rsat,
Page 191 and 192: 178 Figure 6.4: Variation of spectr
Page 193 and 194: visible spectrum are increasing at
Page 195 and 196: 182 Figure 6.5: Munsell plots of La
Page 197 and 198: trying to match color ca from the p
Page 199 and 200: as it ages. This is in direct contr
Page 201 and 202: teractive viewer. In our applicatio
Page 203 and 204: 190 Figure 7.1: Our simulated canva
Page 205 and 206: where n is the normal at the curren
Page 207 and 208: In summary, our implementation prov
Page 209 and 210: Chapter 8 Conclusion We have studie
Page 211 and 212: inks are beginning to find their wa
Page 213 and 214: Appendix A Derivation of K-M theory
Page 215 and 216: ∆i − =(K + S) idx 202 ∆j −
Page 217 and 218: Equation A.8 is now: Rearranging yi
Page 219 and 220: and if the paint is infinitely thic
Page 221 and 222: One concatenates the layers into a
Page 223 and 224: 210 Figure B.1: Cold Glauconite in
Page 225 and 226: Table B.1: Color conversions from t
Page 227 and 228: 214 Figure B.4: Munsell plots of Co
Page 229 and 230: 216 Figure B.5: Burnt Sienna in dif
Page 231 and 232: Table B.5: Color conversions from t
Page 233 and 234: 220 Figure B.8: Munsell plots of La
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222 Figure B.9: Red Ochre Tint in d
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Table B.9: Color conversions from t
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226 Figure B.12: Munsell plots of C
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228 Figure B.13: Variation of spect
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230 Figure B.15: Variation of spect
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Table B.13: Color conversions of Bu
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234 Figure B.18: Munsell plots of C
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236 Figure B.20: Munsell plots of R
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References [Alb71] Josef Albers. In
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240 [GLL + 04] Michael Goesele, Hen
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242 [KM31] Paul Kubelka and Franz M
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[Rat72] Floyd Ratliff. Contour and
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