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

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Looking down the vertical axis of the cylindrical solid yields the polar coordi- nate plot in the bottom-left of the image. This illustrates the hue versus chroma relationship of the eight samples. For the Lapis Lazuli samples, the central ten- dency of the hue is around 2-3PB (purple-blue), as most of the colors lie in that range. Note that the most dissimilar colors (casein and watercolor) are the farthest outlying hues in each opposite direction. The top-right image in the figure can be thought of as a leaf in the solid. It contains the value versus chroma information in a two-dimensional Cartesian plot. In the graph, encaustic and tempera are close in proximity, while casein and watercolor are not. The bottom-right image of the figure provides a closer view of the relationships between the eight colors in three dimensions. A sphere is placed at the point in space where the hue exists in the Munsell color solid. Each sphere has a diffuse material, colored with RGB values converted from the XY Z coordinates in Ta- ble 6.1 using Equation 3.6. The white dots are value-chroma plots of the points projected onto the nearest leaf. The leaves also define the boundary of the dis- playable gamut for a typical CRT display monitor. The Munsell color swatches that are surrounded via a dotted line are unable to be realized by a typical CRT monitor (and thus will not appear as they do in real life). Many of the converted colors from the samples fall in or near this range. The eight spheres are all connected via a series of lines, originating from the acrylic sample. This is to give a sense of the spatial relationship between the points, as there is no easy way to represent the data in only two dimensions. Since a point (casein) lies on the other side of a major hue leaf division, the image is 175 defined to be slightly transparent. A relationship-connecting line between colors i
and j has a saturation of red rsat, such that where rsat = rmaxSat rmaxSat is red with the maximum saturation ∆Ei,j ∆Emax ∆Ei,j is the Euclidean distance between colors i and j in L ∗ a ∗ b ∗ space ∆Emax is the Euclidean distance between the most dissimilar colors in L ∗ a ∗ b ∗ 176 (6.1) Hence, all of the distances are scaled by the largest distance. The more dissimilar colors will have a more vivid red line, while the more alike colors will have paler line colors. Ultimately, the images show a vast amount of data in a very concise setting. The resulting conclusion from this information is that the material that adheres the pigment to the support has a great influence on the resulting color, inciting differences in the multi-dimensional space of hue, value and chroma. The differences are many times that of the threshold of the human observer and easily perceptible from many sources. This includes viewing either the spectral data, coordinates from any of the converted color spaces or even direct observation from photographs. More examples of this behavior for different pigment-time combinations can be seen in Appendix B. 6.1.2 Effect of time In order to study the effect of time on a paint solution, the specific pigment and media are held constant. This allows for comparison of the sample’s different stages as time evolves. In our experiment, there are six time intervals, each with its
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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
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in front of a displayed work. Felle
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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
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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 185 and 186: 172 Table 6.2: Perceptual differenc
Page 187: 174 Figure 6.3: Munsell plots of La
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 233 and 234: 220 Figure B.8: Munsell plots of La
Page 235 and 236: 222 Figure B.9: Red Ochre Tint in d
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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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