bluuebunny/crossref_metadata_2025 huggingface dataset:
Der Aufbau des Tetracyclo[4.1.0.02,4.03,5]heptan‐Systems durch Addition halogensubstituierter Carbene an Benzvalen
Authors: Christl Manfred , Freitag Gertrud , Brüntrup Gisela
Published: June 2007

Aus der Addition von Dibrom‐, Dichlor‐, Difluor‐, Chlorfluor‐ und Chlorcarben an Benzvalen (1) gehen die entsprechenden 7‐substituierten Tetracyclo[4.1.0.02,4.03,5]heptane 2a–g hervor. Ihr hochgespanntes Ringsystem erhält damit den ersten und gleichzeitig ergiebigen Zugang. Mit Ausnahme von Fluor lassen sich die Halogenatome leicht durch Wasserstoff ersetzen, wodurch 7‐endo‐ (2g) und 7‐exo‐Monochlortetracycloheptan (2f) einen zweiten Syntheseweg erhalten, jeweils die beiden Monofluor‐ und Monobromderivate 2k und 1 bzw. 2h und i darstellbar sind und schließlich der unsubstituierte Grundkörper 2m in präparativ brauchbaren Mengen bereitet werden kann. 2m lagert unter Silber(I)‐Ionen‐Katalyse exotherm im Cycloheptatrien um; aus dem Dideuterioderivat 2n entsteht analog isomerenfreies 3,4‐Dideuteriocycloheptatrien (7a). Die 1H‐ und 19F‐NMR‐Spektren enthüllen die vorzügliche Eignung des Tetracycloheptangerüsts zur Vermittlung von Fernkopplungen. Direkte Wechselwirkungen durch den Raum werden im Falle von J4,7endo in Betracht gezogen.
A new Method for the Synthesis of Many‐membered Sulfides by Means of Thioacetamide
Authors: Hammerschmidt Erich , Bieber Wolfgang , Vögtle Fritz
Published: June 2007

Neue Methode zur Synthese vielgliedriger Sulfide mittels Thioacetamid

Ausgehend von Brommethyl‐Verbindungen und Thioacetamiden werden die Sulfide 4–7 durch Umsetzung in wäßrigem — oder besonders vorteilhaft — wasserfreiem Medium in Gegenwart von Basen wie Alkalihydroxiden oder tert‐Butoxid in guten Ausbeuten erhalten. Die Vorteile der Thioacetamid‐Cyclisierung gegenüber dem bisher üblichen Einsatz von Na2S · 9H2O werden herausgestellt.
Darstellung eines Halbylids via Übergangsmetallkomplex
Authors: Kreißl Fritz R. , Eberl Karl , Kleine Willi
Published: June 2007

Synthesis of a Half Ylide ria Transition Metal Complex

A novel cationic half ylide [Ft2NC(PMe3)2][BF4] can be obtained by reaction of trimethylphosphine with the cationic carbyne complex [(CO)5CrCNEt2][BF4] followed by cleavage of the metal carbon σ‐bond. A mechanism is proposed which suits the experimental facts.
Synthese eines bifunktionellen Spin‐Labels zur Quervernetzung von Proteinen
Authors: Wenzel Herbert R. , Becker Gabriele , von Goldammer Eberhard
Published: June 2007

Synthesis of a Bifunctional Spin‐label for Cross‐linking of Proteins

The nitroxyl radical 4 of the pyrrolidine series with two functional iodoacetamido groups was synthesized. It appears to be useful for cross‐linking of proteins and subsequent conformational studies by the ESR method.
Beiträge zur Chemie des Bors, XCIV: Zur Darstellung organylsubstituierter Hexahydrotetrazadiborine
Authors: Nölle Dieter , Nöth Heinrich , Winterstein Wolfgang
Published: June 2007

Contributions to the Chemistry of Boron, XCIV: Preparation of Organylsubstituted Hexahydrotetrazadiborines

The reactions of diorganylhydrazines R′NHNHR′ with either RB(SCH3)2 or (CH3)2B2S3 yield the title compounds.
Radikalionen, XX: Die hyperkonjugative Stabilisierung von p‐Xylol‐Radikalkationen durch (H3C)3Si‐Substituenten
Authors: Back Hans , Kaim Wolfgang , Rohwer Hans E.
Published: June 2007

Toluol‐ und p‐Xylol‐Derivate mit α‐Si(CH3)3‐Gruppen (1–6) verdeutlichen die beträchtliche Stabilisierung von Radikalkationen durch π‐Hyperkonjugation mit CSi‐Bindungen: Die [(H3C)3Si]nCH3−n‐Substituenten erniedrigen besonders die 1. Ionisierungsenergie stark und sind in ihrer Wirkung etwa H3CO‐ oder H2N‐Gruppen vergleichbar. Alle p‐Xylol‐Derivate besitzen IE1 < 7.8 eV und lassen sich auch mit AlCl3 in H2CCl2 oxidieren. Die hochaufgelösten ESR‐Spektren der erzeugten Radikalkationen belegen weitgehende Spindelokalisation in die [(H3C)3Si]nCH3−n‐Gruppen. Die Winkelabhängigkeit der Kopplungskonstanten stützt die postulierten σCSi/π‐hyperkonjugativen Wechselwirkungen, und ihre Temperaturabhängigkeit liefert Informationen über die Substituentenbeweglichkeit in den sterisch überfüllten Radikalkationen.
Beiträge zur Chemie des Bors, XCVI: Die N‐Metallierung N‐substituierter Aminodimethylborane mit Organolithium‐Verbindungen
Authors: Fußstetter Hermann , Nöth Heinrich
Published: June 2007

In der Reihe (CH3)2BNHN(CH3)2(1), BNHSi(CH3)2BNHB(CH3)2 (7) gewinnt die Lewis‐Acidität der (CH3)2BN‐Gruppe im Vergleich zur Protonenacidität der NH‐Gruppe gegenüber Lithiumorganylen zunehmend an Gewicht. N‐Lithioderivate (2, 5) sind nur mehr von 1 und 4 darstellbar. NMR‐spektroskopisch ist bei allen Reaktionen mit LiCH3 die Boratstufe [(CH3)3BNHR]Li (3, 6, 8) nachweisbar, die bei 3 und 6 unter Methanabspaltung, bei 8 hingegen zu LiB(CH3)4 und (CH3BNH)3 zerfällt. Die NMR‐Spektren der N‐Lithioaminoborane 2 und 5 belegen eine Bindungsordnung > 1 für die BN‐Bindung. Nach Massenspektren dürfte 5 hexamer und 2 polymer aufgebaut sein.
Konfiguration und cis‐Effekt bei Diphenyl‐(oxa)bicyclo[4.2.0]octanen
Authors: Kaupp Gerd , Stark Michael , Fritz Hans
Published: June 2007

Die Photoadditionen von trans‐Stilben an elektronenreiche Alkene (z. B. 2b, 4d u.a.) werden im Hinblick auf mit dem üblichen Zweistufenmechanismus nicht vereinbare Literaturangaben bei 4d untersucht. Im Gegensatz zu Literaturangaben sind die Photoaddukte cis‐verknüpft und besitzen trans‐ständige Phenylgruppen. Die Photolyse der verschiedenen Stilbenaddukte folgt dem bei zweistufigen Vierringspaltungen gültigen cis‐Effekt. Die beträchtlichen Selektivitätsvariationen werden diskutiert. Hinweise auf die Strukturen und Gleichgewichte von Konformeren werden aus Molekülmodellen, der Feinstruktur von UV‐Spektren und Fluoreszenzdaten gewonnen. Neben den Vierringspaltungen werden in den meisten Fällen schon bei −190°C geometrische Isomerisierungen beobachtet. Einige bifunktionelle Styrylenolether‐Derivate werden isoliert und z. T. der intramolekularen [2 + 2]‐Photocycloaddition unterworfen. Als Sonderfall wird bei der Belichtung von 14 eine neue [4 + 2 + 2]‐Photocycloreversion beobachtet.
Übergangsmetall‐Carbin‐Komplexe, XLIII: Reduktion einer Metall‐Kohlenstoff‐Dreifachbindung
Authors: Fischer Ernst Otto , Frank Albin
Published: June 2007

Transition Metal Carbyne Complexes, XLIII: Reduction of a Metal‐Carbon Triple Bond

Reaction of [π‐C5H5(CO)2ReCC6H5]+[BCl4]− with Et2AlH yields — depending on reaction conditions — the novel secondary carbene complex π‐C5H5(CO)2ReCHC6H5 (2) or the σ‐benzylhydrido complex π‐C5H5(CO)2HReCH2C6H5 (3). The reaction is the first example of a stepwise reduction of a metal‐carbon triple bond to a single bond.
Darstellung von Vinylisothiocyanaten durch Schwefel‐Eliminierung aus Δ3‐1,3‐Thiazolin‐2‐thionen
Authors: Hussein Ahmad Q. , Abu‐Taha Ahmed , Jochims Johannes C.
Published: June 2007

Syntheses of Vinyl Isothiocyanates by Sulfur Elimination from Δ3‐1,3‐Thiazoline‐2‐thiones

The Δ3‐thiazoline‐2‐thiones 1a, b eliminate sulfur thermally, photolytically, or with trimethyl phosphite to give the vinyl isothiocyanates 2a, b. Compound 2a forms a thiosemicarbazone 3a which cyclizes thermally to 4. This easily splits off the isopropyl group to give the triazolinethione 5. The vinyl isothiocyanate 2b rearranges thermally or photochemically to the isoquinoline‐1‐thione 7 which itself is photolabile.
Bildung, Struktur und Reaktivität von (Pentafluorphenyl)bor‐tert‐butylimid und seinem Cyclodimeren
Authors: Paetzold Peter , Richter Anette , Thijssen Theo , Würtenberg Stefan
Published: June 2007

Bei der Gasphasenthermolyse der Aminoborane RB(Cl)‐N(SiMe3)R' (la–j) bei 500–600°C erhält man neben Me3SiCl entweder die Borazine (RBNR')3 (3a–f) oder die Diazadiboretidine (RBNR')2 (2g–h) oder das Borimid C6F5–B = N–tBu (4i) oder ‐ im Falle R' = Mesityl – das bicyclische Produkt eines intramolekularen Ringschlusses 5. 4i dimerisiert bei Raumtemperatur ohne Lösungsmittel schnell, in Lösung weniger rasch zu seinem Cyclodimeren 2i. Dieses kristallisiert in der Raumgruppe C2/c. 2i erfährt mit Ketonen im Verhältnis 1:1 eine enolytische Ring‐öffnung (6i,6í). Die CO‐Bindung ungesättigter Aldehyde schiebt sich in den Vierring von 2i unter Sechsringbildung (7i, 7í) ein. Mit PhHC = N(O)Me setzt sich 2i unter Abspaltung von PhHC = NtBu zum Oxadiazadiborolidin 9i um. IR‐ und NMR‐spektroskopische Befunde sprechen sowohl für eine BN‐Bindungsordnung größer als zwei als auch für BC‐π‐Wechselwirkungen in der Titelverbindung 4i. Mit Ph2C = O reagiert 4i analog zur Wittig‐Reaktion zu (C6F5BO)3 und Ph2C = NtBu und dieses geht mit 4i quantitativ eine [2 + 2]‐Cycloaddition zu 10i ein. Mit Cyclopentadien setzt sich 4i als Dienophil im Sinne einer Diels‐Alder‐Reaktion zu 11i um.
Bausteine von Oligosacchariden, XVIII. Synthese von 4‐O‐Aminosäure‐ und 4‐O‐Carbamidsäureestern von Garamin
Authors: Paulsen Hans , Böttcher Henning
Published: June 2007

2′,4′,5‐Tri‐O‐benzyl‐l,2″,3,3′,6″‐pentakis‐N‐(benzyloxycarbonyl)gentamicin C (7) läßt sich selektiv mit Trifluoressigsäure 2′,4′,5‐Tri‐O‐benzyl‐1,3,3′‐tris‐(N‐benzyloxycarbonyl)garamin (13)spalten. Die unsubstituierte 4‐OH‐Gruppe von 13 wird in die Ester 16–19 und über das Imidazol‐Derivat 20 in die Carbamidsäureester 21–26 übergeführt. Hydrogenolytische Entblockierung liefert in einem Schritt die freien 4‐O‐Aminosäure‐ und 4‐O‐Carbamidsäureester des Garamins 29–31 und 32–38.
Notizen. Synthese und Eigenschaften von Lithium‐tetrakis(trimethylsilyl)aluminat‐Komplexen
Authors: Rösch Lutz , Altnau Gerald
Published: June 2007

Synthesis and Properties of Lithium Tetrakis(trimethylsilyl)aluminate Complexes

Chlorotrimethylsilane reacts with aluminium and lithium in ether in the presence of mercury to form lithium tetrakis(trimethylsilyl)aluminate, coordinated with diethyl ether, tetrahydrofurane, or dimethoxyethane. Unsolvated lithium tetrakis(trimethylsilyl)aluminate results by repeated sublimation of the ether adduct. The IR, Raman, and NMR spectra are discussed.
Analyse des Makro‐ und Mikromischens mit Hilfe von laserdiagnostischen Verfahren
Authors: Faes M. , Glasmacher B.
Published: June 2007

In vielen Bereichen der chemischen, pharmazeutischen und Lebensmittelindustrie zählen Mischprozesse zu den am häufigsten eingesetzten Verfahren. Trotz ihrer häufigen Anwendung ist es bisher jedoch noch nicht gelungen, die Zusammenhänge zwischen dem konvektiven Transport im Strömungsfeld, dem diffusiven Transport un d der Kinetik einer chemischen Reaktion vorauszusagen. Dazu sind experimentelle Untersuchungen durchzuführen, die eine Betrachtung der Transportmechanismen in einem Mischprozess auf unterschiedlichen Skalen erlauben. Für die Untersuchungen der ablaufenden Transportphänomene auf der Makro‐ und Mikroskala werden zwei laseroptische Verfahren eingesetzt, die eine Kopplung der zu betrachtenden Prozesse gewährleisten.
Beanspruchung von Partikeln und Fluidelementen beim Rühren
Authors: Wollny St. , Sperling R. , Kraume M. , Ritter J.
Published: June 2007

In Fermentationsanlagen können tierische Zellen durch mechanische Beanspruchungen irreversibel geschädigt werden, wodurch die Produktivität sowie die Produktreinheit sinken. Da solche Fermentationsprozesse häufig in Rührreaktoren bewerkstelligt werden, sind numerische und experimentelle Untersuchungen zur Klärung der physikalischen Effekte für die Prozessgestaltung/‐optimierung von Nutzen.
Aktuelle Entwicklungen in der CFD für gerührte Systeme
Authors: Paschedag A. R. , Kassera V. , Sperling R.
Published: June 2007

Computational Fluid Dynamics (CFD) ergänzt auch in der Verfahrenstechnik und speziell in der Rührtechnik zunehmend experimentelle Untersuchungen und klassische Auslegungsregeln beim gezielten Design und der Optimierung von Apparaten. Die Vorzüge liegen einerseits in der Bereitstellung ortsaufgelöster Informationen, die benötigt werden, um z. B. lokale Überhitzungen oder kritische Scherbeanspruchungen zu vermeiden, die messtechnisch nicht oder nur mit großem Aufwand zugänglich sind. Andererseits können Parameterstudien mit CFD oft preiswerter durchgeführt werden als experimentelle Untersuchungen. Der Beitrag dokumentiert Entwicklungen der letzten Jahre, die den Einsatz der CFD auch für industrielle rührtechnische Anwendungen sinnvoll gemacht haben. Schwerpunkte liegen auf der Modellierung der bewegten Einbauten, der Turbulenzmodellierung, der Behandlung nicht‐Newtonscher Fluide und der Simulation von Mehrphasenströmungen.
Verification of a front‐tracking model of two‐fluid interface Kelvin–Helmholtz instability by study of travelling waves
Authors: Tong Mingming , Browne David J.
Published: June 2007

A novel travelling wave case study is developed to verify a front‐tracking model of Kelvin–Helmholtz (K–H) instability of immiscible, incompressible two‐fluid flow. In this benchmark comparison, two fluids flow at different velocities in the same parallel horizontal direction, forming travelling waves when the interface between the fluids is set to oscillate in the vertical direction at the inlet. With a specific oscillation frequency, the effect of the inlet velocity difference, or gap, on the interface undulation spatial propagation, such as wave damping or wave amplification is quantitatively analysed. By using a variety of different inlet velocity gaps and oscillation frequencies, the effects of the gap on wave propagation are investigated over a large range of wave numbers. The simulation predictions are compared with the result of the linear stability theory. This comparison represents a comprehensive verification of the current front‐tracking model of K–H instability. Copyright © 2007 John Wiley & Sons, Ltd.
Exhibiting artwork: Consider the illuminating source
Authors: Berns Roy S. , Grum Franc
Published: June 2007

This article describes the steps that should be considered for the proper illumination of artwork. In particular, our intent is to show how a different illuminating environment from one intended by the artist affects the color appearance of exhibited paintings. Using five different illuminants and several illumination levels, it is shown for eight artists' pigments that large color‐appearance differences occur. This is true even after the effects of chromatic adaptation are taken into account.
Visual thresholds measured with color video monitors
Authors: King‐Smith P. Ewen , Vingrys Algis J. , Benes Susan C.
Published: June 2007

We describe the types of threshold measurement that can be made by using a circular test spot whose colorimetric, temporal, and spatial parameters can be varied. Examples are given of the application of a number of these tests to studies of normal and clinical vision.
Color space of the coloroid color system
Authors: Nemcsics Antal
Published: June 2007

The Coloroid color system is a Hungarian standard color order system. This article describes the color space of the Coloroid system and its relationship to the CIE colorimetric space and the spaces associated with the Munsell and DIN color order systems. The Coloroid system is presented as a compromise of principles of uniformity in regard to color difference and color harmony, as well as ease of mapping into the CIE colorimetric space.
The color specification of scottish tartans
Authors: Sinclair Roy S.
Published: June 2007

The methods used by the Scottish Museum of Tartans for recording the yarn count and color specifications of tartans are described. The origin of the colors used in old tartans has been investigated by preparing dyeings on wool using extracts from a large number of plants native to Scotland. The colors so obtained have been recorded, and a selection of the results is presented in terms of CIELAB coordinates and compared with the colors obtained from the well‐known natural dyes of the past. The changes in color caused by fading have also been recorded and the results analyzed to clarify the origin of the colors used in the modern, ancient, and reproduction tartans manufactured today.
Color vision theories in nineteenth century germany between idealism and empiricism
Authors: Lang Heinwig
Published: June 2007

Helmholtz and Hering are well known names in the history of physiological optics and color‐vision theory, whereas Goethe's work on color is generally regarded as standing outside the mainstream of scientific tradition. This article shows that Goethe not only stimulated the philosopher Schopenhauer to publish on color vision, but also Purkyňe and Johannes Müller, then the most influential authorities writing on sensory physiology in Germany. The latter was Helmholtz's teacher. The treatment of subjective color‐contrast phenomena by different German nineteenth‐century authors reflects the conflict between idealism and empiricism. In Germany idealism had an overwhelming influence on scientific ideas and institutions at the beginning of the last century. After 1830 this influence declined rapidly and was replaced by empiricism. But some of the idealistic stimulations remained active until the end of the century, especially in the work of Fechner and Hering.
The influence of spectral bandpass on accuracy of tristimulus data
Authors: Stearns E. I.
Published: June 2007

When calculating tristimulus values from spectral radiance factors which were measured with a spectral bandpass of 10 nm, using data from the same specimen measured with a spectral bandpass of 1 nm and calculated with a 1‐nm interval as standard, and evaluating the significance of the difference in tristimulus values with the CIELAB color difference formula, it is highly probable that a 1‐nm calculation interval will give no greater accuracy than a 10‐nm calculation interval. For this reason it is recommended that the CIE reconsider their approval of the deletion of the 10‐nm calculation interval from the new edition of Publication CIE 15.
A Painter's thoughts on color and form
Authors: Osborne Roy
Published: June 2007

Like that of many art students, my initial training seemed dominated by linear drawing, so that painting too often became a matter of outlining shapes and then coloring them in. It was not until I more closely studied the work of Cézanne. Seurat, Robert Delaunay, and other great colorists, that I gained more insight into how color might be used independently of drawing, of how color could create its own form and ultimately become a subject of artistic experiment in its own right. This article examines one artist's thoughts on the relationship between drawing and color, set within a wider, art‐historical context.
Modeling the mixing behavior of inks with polynomials
Authors: Vachon Guy
Published: June 2007

A technique for developing equations to predict the color of an ink combination is described. A complete characterization of a printing process inherently requires a great deal of data. It is possible to fit higher‐order polynomials to ink data. Pobboravsky fit ink data by optimizing polynomials through linear regressions with limited success. The techniques described depict and overcome the limitations of previous attempts at modeling the ink mixing behavior with polynomials.
Colour‐distance judgement and the influence of the background in colour reproduction
Authors: Schultz Ursula
Published: June 2007

The influence of the background in colour reproduction can be described in colorimetric terms by the use of corrections to the colorimetric scaling factors. This leads to transformation formulae that describe the change of chromatic adaptation, and also to an extended definition of the so‐called “colour of the state of chromatic adaptation.” The method leads to an improved reconciliation between the specification of colour‐rendering properties in both colour photography and multicolour printing and the visual evaluation. Certain problems in colorimetry may also become more easily understandable by the incorporation of such peripheral influences. Whereas the physiologically related scaling‐factor corrections are of first‐order importance, it is shown that stray‐light effects, which are physical contributing factors, are only of the second order.
Spectral tuning of opponent channels is spatially dependent
Authors: Finkelstein Marcia A.
Published: June 2007

Psychophysical detection and appearance data suggest that the spectral tuning of opponent pathways varies with test size. The present study examines the effect on spectral sensitivity of the relative size of test and surround fields. Increment thresholds and flashed‐field sensitivities were obtained for 580 nm and 641 nm targets. Three spatial configurations were used. The pattern of sensitivity loss is shown to depend on the spatial relation between test and field; the effect of the spatial relation in turn depends on test wavelength. The findings are explained by the activity of a changing network of spatially and spectrally opponent cells.
Recursive quadratic programming algorithm for color matching
Authors: Cogno J. A.
Published: June 2007

A recursive quadratic programming (RQP) algorithm for color matching is described. RQP does not work on the assumption that the difference of spectral reflectance between sample and match can be approximated by a first‐order expansion. Color matching is instead obtained only by agreement of a trichromatic specification. A numerical example showing a possible field of application of RQP is presented.
From softcopy to hardcopy on a desert island
Authors: Brill Michael H. , Panken Neal
Published: June 2007

A computer program is written that converts from a digital color image (driving the phosphors of a softcopy video display) to the areal dye densities for a halftone hardcopy device. The program is intended to be generic enough for acceptable color reproduction between a variety of devices without slavish attention to such factors as the phosphor and dye spectra. Only one parameter called “subtractiveness” is empirically adjustable depending on how much image darkening must be compensated. No particular theory is invoked, but the transformation between RGB inputs and CMY outputs is constrained to ensure (1) symmetry among the image planes; (2) no higher than third‐degree polynomials; and (3) nominal correspondence of the eight extremal colors red, green, blue, cyan, magenta, yellow, white, and black. When tested on one set of devices, the program works well enough for the “desert islands” inhabited by most users.
Scaling procedures for specifying color appearance
Authors: Gordon James , Abramov Israel
Published: June 2007

Colors of objects are often specified by color matches in some standard colorimetric system. While color‐matching allows a color to be reproduced accurately, it does not specify what the color actually looks like. Color appearance (i.e., hue, saturation, brightness) can be measured by direct psychophysical scaling techniques; however, these methods have not been standardized and have been confined mostly to the laboratory. We have examined several variants of continuous, numerical scaling of hue and saturation to find a procedure that is usable, even by untrained observers. Appearances of monochromatic, equal‐luminance light flashes were scaled along the dimensions of the unique hue sensations (red, yellow, green, blue) and apparent saturation. These functions were obtained for various stimulus conditions, including changes in stimulus luminance, size, and eccentricity. Multidimensional scaling methods were used to derive metrically uniform color appearance diagrams from the hue and saturation scaling data. Validity of the scaling procedures was assessed by deriving well‐known visual functions, such as wavelength discrimination, from the color appearance diagrams. The direct scaling method was shown to be generally useful, and both trained and untrained observers readily and reliably used the technique.
Large colour differences measured by spontaneous gestalt formation
Authors: Stalmeier Peep F. M. , De Weert Charles M. M.
Published: June 2007

Gestalt formation is used as a means to measure large colour differences. The stimulus is presented in the form of the Star of David, being made of two overlapping triangles of different colour, with the overlap being in a third colour. Through Gestalt formation the subjects perceive a triangle pointing to the left or to the right. Gestalt formation is assumed to occur for colour combinations with the smallest perceptual distance. We simulated responses at the ordinal level with several uniform‐colour‐distance models, derived from near‐threshold colour‐discrimination experiments. For isoluminant colours 84% of the responses, and for nonisoluminant colours 76% of the responses, are predicted correctly by the best model. We argue that the tritanopic direction is crucial for the understanding of large‐colour‐difference data.
Background stimulus for invariant spectral sensitivity
Authors: Fuld Kenneth , Sparrow John E. , Daning Robin , Slade Carolyn W.
Published: June 2007

Increment‐threshold spectral sensitivity was determined with backgrounds of four different chromaticities and two different troland (td) levels. One background was equivalent to a field delivering to the receptors an equal quantal flux at all visible wavelengths. Another background approximated CIE Illuminant A. Light from a chromatically unfiltered xenon‐arc lamp provided a third background. The fourth background was monochromatic at 470 nm. Backgrounds were presented at 10 and 1000 td. Foveal spectral sensitivity determined on each of these backgrounds was compared to that measured for the dark‐adapted state. The 10‐ and 1000‐td equal‐quantal fields yielded the functions that most closely approximated the curve resulting from the dark‐adapted condition, suggesting that such an equal‐quantal field, which appeared as a saturated blue, is neutral for measurements of spectral sensitivity. Because of the putative contribution of the opponent chromatic channels to spectral sensitivity determined using increment thresholds, the results further suggest that at the detection stage of these channels an equal‐quantal field provides a balanced state of adaptation.
Color coding for rapid location of small symbols
Authors: Carter Robert C. , Carter Ellen C.
Published: June 2007

Color coding for small symbols is discussed. An exploratory study of visual search on an electronic display is described. Colors of small symbols (subtending less than 30′) are less distinct than those of 1° and 2° symbols. The study shows that surround luminance is a factor having its own effect that also alters the effect of symbol size on color perception. Human performance using small symbols is better when target symbols have a larger color difference (CIELUV) from both distractor symbols and the surround. The effect of reduced symbol size is accentuated by differences between surround luminance and symbol luminances. To predict human performance in tasks requiring rapid location of small symbols, one should consider surround and symbol luminances as well as color differences.
Empirical modeling of systematic spectrophotometric errors
Authors: Berns Roy S. , Petersen Kelvin H.
Published: June 2007

Spectrophotometers, as electro‐mechanical‐optical devices, perform at a finite level of accuracy. This accuracy is limited by such factors as monochromator design, detector linearity, and cost. Generally, both the diagnosis and correction of spectrophotometric errors require a number of calibrated standard reference materials and considerable effort and commitment on the part of the user. A technique using multiple linear regression has been developed, based on the measurement of several suitably chosen standard reference materials, to both diagnose and correct systematic spectrophotometric errors, including photometric zero errors photometric linear and nonlinear scale errors, wavelength linear and nonlinear scale errors, and bandwidth errors. The use of a single chromatic ceramic tile to correct systematic errors improved the colorimetric accuracy of a set of chromatic and neutral tiles by a factor of two for a typical industrial‐oriented spectrophotometer. Greater improvement can be achieved by increasing the number of tiles and performing a separate regression at each measured wavelength., These techniques have been extremely useful in improving inter‐instrument agreement for instruments with similar geometry.
Quantification of illuminant metamerism for four coloration systems via metameric mismatch gamuts
Authors: Berns Roy S. , Fairchild Mark D. , Beering Michael M.
Published: June 2007

Illuminant metamerism was evaluated by generating achromatic metamers for an acrylic‐enamel coating, an acrylobutadiene styrene polymer, a polyester textile, and a nylon textile using computer colorant formulation techniques. The tristimulus matching algorithm used to generate the metamers was based on Kubelka‐Munk turbid media theory. By definition, each set of metamers that were formulated to match under CIE illuminant D65 for the 1964 CIE standard observer would mismatch under a test illuminant, forming a gamut of colorimetric coordinates. These metameric mismatch gamuts were evaluated quantitatively using multivariate statistics. Illuminants A, F2, and F11, representing incandescent, cool‐white fluorescent, and narrow‐band fluorescent, respectively, were used as test illuminants. Illuminant similarities, coloration system similarities, tristimulus variability, and reference illuminant selection criteria were evaluated.
Spectral tuning of opponent pathways is temporally dependent
Authors: Finkelstein Marcia A.
Published: June 2007

Psychophysical test and field sensitivity data suggest that the spectral sensitivities of red/green opponent channels (red/green cells) become progressively nonopponent with decreases in stimulus size or duration. Recent data show that the shape of the field sensitivity depends not on field size per se but on the relative size of test and field. The present study examined the effect on field sensitivity of variations in the temporal parameters of stimulation. The results suggest a more complicated interaction than is observed in the spatial domain. Spectral tuning depends not only on the relative durations of test and field but also on the offset asynchrony between the two lights. Only when the test is extinguished prior to the field do the data show evidence of red/green activity. When the two lights coterminate. the field sensitivity resembles a nonopponent function, regardless of stimulus duration.
Chromatic adaptation on the minimally distinct border and brightness matching in color‐normals and deuteranopes
Authors: Hibino Haruo , Oyama Tadasu
Published: June 2007

We examined the effect of monochromatic adapting lights on minimally distinct border (MDB) settings and brightness matching (BM) between monochromatic test and reference fields by using three color‐normals and three deuteranopes as observers. In the case of MDB, for color‐normal observers chromatic adaptation appeared prominetly in the wavelength regions near the test and reference wavelengths in the corresponding field, when either the test or reference field was in the long‐wavelenth region. No differential effect was found for deuteranopic observers. Using BM instead of MDB, the differential effects of chromatic adaptation appeared more prominently in the short‐wavelength region for both types of observers (especially for color‐normals) and in the middle‐wavelength region for color‐normal observers. The results indicate that the blue‐sen‐sitive mechanisms make either little or no contribution to the MDB criterion, or the distinctness of borders.
Performance testing of color‐difference metrics using a color tolerance dataset
Authors: Alman David H. , Berns Roy S. , Snyder Gregory D. , Larsen Wayne A.
Published: June 2007

A color‐difference dataset was developed for testing the performance of color metrics. The dataset comprises 45 color‐difference vectors varying in five directions at nine color centers under conditions typical of commercial color decisions. Probit analysis was used to estimate the parameters of the population distribution of tolerances for each vector. In addition to estimating the median tolerance, the anlysis allows one to estimate the uncertainty of a tolerance and to test the adequacy of the underlying model tolerance distribution. The median tolerances were used to specify 45 color‐difference pairs with equal visual color‐difference magnitudes. The performance of eight color‐difference metrics was compared using the normalized standard deviation of the color differences of the visually equal difference pairs as a measure of uniformity. A bootstrap statistical technique was used to quantify the variation in performance with varying samples of color centers and color‐difference directions and to determine the significance of observed differences in uniformity performance. Some metrics based on weighted CIELAB dl*, dC*, dH* color‐difference components had significantly superior performance compared to the CIE recommended color‐difference metrics.
Color vision model of macLeod and Boynton
Authors: Fry Glenn A.
Published: June 2007

MacLeod and Boynton started off with the assumption that the fundamental blue falls on the x' axis of Judd's 1951 chromaticity diagram. This leads to a constant luminance diagram in which the lines that converge at the fundamental blue in Judd's diagram are parallel. MacLeod and Boynton tried to solve this problem by a slight change in one of the constants in the transformation equations. It turns out that what this does is to shift the position of the alychne on Judd's diagram so that it does not coincide with the x' axis. The blue fundamental no longer lies on the alychne. This makes it possible to derive a constant luminance chromaticity diagram in which the fundamental blue falls at one of the corners. After having created this new diagram, they used it to formulate a theory of color vision in which the blue cones contribute nothing to luminance. This procedure needs to be understood because it can be used to convert any theory of color vision in which all three cones contribute to luminance to one in which only two contribute to luminance. This has nothing to do with having the blue fundamental fall on the x' axis. A more serious problem is that Judd has made an error in his assessment of the luminosity coefficients and the concepts of MacLeod and Boynton need to be reformulated in terms of the CIE 1931 chromaticity diagram.
Changes in the wavelength of unique yellow with retinal angle of incidence
Authors: Geri George A. , Kandel Gillray L. , Roy Ii C. Genter , Walker Karen L. , Rowan Melena A.
Published: June 2007

The wavelength associated with the perception of unique yellow was determined for various retinal angles of stimulus incidence. Techniques previously used to measure the Stiles‐Crawford (SCII) hue shift as a function of retinal angle of incidence were procedurally and instrumentally complex and, as a result, data from only two observers exist in the literature. A simpler technique is used here to obtain data from six observers, two of whom showed hue shift functions qualitatively different from those previously reported. The peak locations of the four typical SCII hue shift functions were found to correlate well with the peak locations of the π4 and π5 color mechanisms previously reported for the same observers. It is argued that peak location is the most valid indicator of the relationship between the Stiles‐Crawford effects of the first (SCI) and second (SCII) kind and that common processes underlie the two effects.
Equivalent lightness of colored objects at illuminances from the scotopic to the photopic level
Authors: Ikeda Mitsuo , Huang Chian Ching , Ashizawa Shoko
Published: June 2007

Equivalent lightness of four colored objects, blue, green, yellow, and red, was obtained for illuminance levels covering the range 0.01 to 1000 lx by brightness matching to a grey scale. Three field sizes, 20', 1° and 6° arc of visual angle, were investigated. With the smallest size, for which no rod response was expected, the equivalent lightness increased monotonically for incresing illuminance, showing the increasing effect of colorfulness upon brightness. The results obtained with the largest size showed influence from both rods and cones and were interpreted as due to two underlying lightnesses, one lightness based on the achromatic response of rods, cones, or both, and the other lightness based on the chromatic response of cones exhibited as colorfulness.
Accurate tristimulus values from spectral data
Authors: Venable William H.
Published: June 2007

Inter‐instrument color measurement errors of up to 2 CIELAB units are typically introduced in the process of numerically integrating spectrophotometric data to obtain tristimulus values. These errors arise partly from inadequacies in the definition of the tristimulus values themselves, but mainly from failing to take into account the effect the instrument function has on the spectrophotometric data. Through using precise definition of the tristimulus values and through using source‐observer weighting tables tailored to each specific instrument, it is practical to reduce this component of colorimetric error to less than 0.1 CIELAB unit for spectrophotometers with bandwidths up to 20 nm.
Color appearance under conditions of chromatic adaptation and contrast
Authors: Shevell Steven K. , Wesner Michael F.
Published: June 2007

Chromatic adaptation can significantly alter the color appearance of a light. We review measurements of changes in appearance caused by chromatic backgrounds and surrounds. Effects of long‐, middle‐ and short‐wavelength adapting lights are assessed by having observers adjust the physical light in a test patch to maintain a constant perceptual criterion: a test that appears neither reddish nor greenish. A variety of spatial and temporal stimulus configurations also is considered. An integrated account of the measurements is provided by the two‐process theory of chromatic adaptation, originally proposed by Hurvich and Jameson in 1958, which specifies an adapting light alters receptoral sensitivities and, simultaneously, contributes an additive increment to opponent chromatic responses.
The computation of color constant descriptors in chromatic images
Authors: Gershon Ron , Jepson Allan D.
Published: June 2007

We propose a method, based on finite‐dimensional linear models of reflection and illumination, which allows the transformation of chromatic images into color constant images. This proves to be useful in applications in which either there is no information on the illuminant present in the scene, or when such information is confounded by the existence of inter‐reflections between objects. The method proposed in this paper is aimed at computations taking place beyond the sensory level of vision systems, and may use inputs corrected by sensors (for adaptation). In contrast to previous work, we show that good results can be obtained using a 3‐receptor system and some knowledge about the spectral properties of natural materials and illuminants. In the method developed, an estimate of the illuminant in the scene is computed, which allow the computation of color constant descriptors of the pixel values in the image. In addition, we show a method of computing an estimate to the actual reflectances of the materials in the scence out of the computed color constant descriptors.
What determines crossover wavelengths of metameric pairs with three crossovers?
Authors: Berns Roy S. , Kuehni Rolf G.
Published: June 2007

Two matameric stimuli with identical tristimulus values must have spectral radiance distributions that cross at least three times. Many studies have shown that the crossover locations of three‐crossover metamers tend to occur in certain defined regions. This finding has led to hypotheses concerning fundamental aspects of the visual system. In the current article, calculations are reported that prove that crossover locations depend on the spectral properties of the metameric stimuli. For object colors, the spectral properties are determined by colorant obsorption bandwidths. Depending on the absorption bandwidth, crossovers can occur in nearly any region of the visible spectrum. Thus any relationship between crossover wavelengths and properties of the visual system such as maximal responsivities appears coincidental.
The munsell color system in fundamental color space
Authors: Burns Scott A. , Cohen Jozef B. , Kuznetsov Edward N.
Published: June 2007

The Munsell color system is investigated as a structure in fundamental color space. The entire collection of samples from the 1929 Munsell Book of Color is mapped into fundamental color space and surfaces of constant hue, value, and chroma are identified. An algorithm, based on these surfaces, is presented for estimating the Munsell specification of an arbitrary reflectance curve.
Colors do look different after a lens implant!
Authors: Granville Walter C.
Published: June 2007

This note describes how colors of some familiar objects and scenes shift when viewed with one of the author's eyes after a lens implant compared to the other eye without implant. Estimates of the shifts are described with common color names. Some shifts were found to be spectacular! Variations in the spectral transmission of the lens is believed to explain the shifts. Implications affecting the choice of clors for interiors, fashions, and other design uses are discussed. An appendix contains data on matches on the Glenn and D & H Color Rules.
A visual colorimeter for atmospheric research
Authors: Henry Ronald C. , Matamala Luis
Published: June 2007

This article describes the design, construction, and evaluation of a visual colorimeter for use in studies of color perception in the natural environment. The colorimeter is portable, has a low power consumption, and produces luminances typical of those found outdoors. An asymmetric binocular‐matching procedure is used to match the colors of natural objects. The performance of the colorimeter was tested by comparing chromaticities of matches of colored papers to spectrophotometric measurements.
Metric coefficients for chromatic discrimination of surface colors
Authors: Melgosa M. , Romero J. , Hita E.
Published: June 2007

The values of the coefficients of the metric tensor (g11, g22, and 2g12) have been determined graphically at any point on the CIE‐1964 chromatic diagram, by using Luo and Rigg's chromatic discrimination data. Chromatic‐discrimination thresholds obtained by this method and those predicted by the CIELUV, CIELAB; and LABNHU color‐difference formulas are compared with different sets of experimental results. The predictions made by the formulas do not fit the experimental results as well as the graphical predictions.
Industrial color difference: Progress and problems
Authors: Kuehni Rolf G.
Published: June 2007

In the ten years since the last Inter‐Society Color Council conference on color discrimination considerable progress in industrial color‐difference evaluation has been made. The results of a questionnaire indicated that the efforts of the CIE to make formula usage more uniform has been successful. Efforts to improve the correlation between average visual judgment and calculated color difference have also resulted in progress. Nevertheless, a considerable amount of work remains to be done regarding the mechanisms affecting color‐difference evaluation before instrumental color‐difference evaluation can become a highly reliable tool of manufacturing.
Equivalent lightness of colored objects of equal munsell chroma and of equal munsell value at various illuminances
Authors: Ikeda Mitsuo , Ashizawa Shoko
Published: June 2007

Equivalent lightness was determined for 26 colored surfaces by heterochromatic brightness matching with a grey scale. The illuminance for observation was varied from 0.01 to 1000 lx to cover scotopic, mesopic, and photopic vision, and the equivalent lightness‐versus‐log illuminance curve was obtained for every stimulus. The shape of the curves did not change if the surfaces had the same Munsell hue and chroma. It differed significantly if they had different hues or different chroma. The curves were interpreted in terms of achromatic lightness and chromatic lightness, which are both subject to change with illuminance level. The achromatic lightness was assumed to follow the Purkinje shift and the chromatic lightness monotonically increased with illuminance. The chromatic lightness was larger for larger Munsell chroma within a single hue.
Theory of primary colors and invariant hues
Authors: Pridmore Ralph W.
Published: June 2007

Additive primaries or peaks of color‐matching functions are defined as peaks of complementary efficiency and of saturation per watt. These are near 447, 532, and 607 nm for all CIE illuminants. (CIE 1931 r, g, b functions peak at 447, 543, and 604 nm.) Subtractive or colorant primaries are defined as saturation minima and peaks of brightness or lightness per watt. Additive and subtractive primaries (e.g., red and cyan) are complementaries and opposites in saturation and lightness. In equal radiance color‐space the six lines of constant mean saturation are invariant hues (473, 508, 574 nm and 558 c) and their complementaries.
Quantifying colour appearance. Part II. Testing colour models performance using lutchi colour appearance data
Authors: Luo M. Ronnier , Clarke Anthony A. , Rhodes Peter A. , Schappo André , Scrivener Stephen A. R. , Tait Chris J.
Published: June 2007

The acquisition of the LUTCHI Colour Appearance Data has been described in Part I of this article. Having obtained the data, they were used to test the accuracy of prediction for various colour spaces and models. The results clearly indicate that Hunt's 91 model gives the best fit to the visual results of all the models studied. Hunt's 91 has been further refined to improve the fit to the colourfulness results, and this refined model has been designated Hunt‐ACAM (ACAM being the Alvey Colour Appearance Model). The error of prediction from Hunt‐ACAM is close to the typical error that is seen to occur between individuals' results and the mean visual results. This performance is considered to be very satisfactory, and the model is therefore believed to provide a reasonably accurate way of evaluating colour fidelity for various colour reproduction systems. Various chromatic‐adaptation transformations were also compared with three sets of corresponding chromaticities derived from the results of experiments conducted under four conditions of chromatic adaptation. The results are in reasonable agreement with those obtained by Helson et al. [Illum. Eng. 47, 221–233 (1952)] and Lam and Rigg [Ph.D. thesis, University of Bradford (1985)]. All results indicate that the Bradford and Hunt‐ACAM transformations perform the best and the second best, respectively, of all the selected formulae. The current CIE recommendation does not perform as well as expected.
The chevreul color system
Authors: Heila Ethel
Published: June 2007

Chevreul wished to represent in his color system every modification of color, including not only the modifications we observe from pigment mixtures but also those modifications in color that we observe in nature. The latter include the various gradations of light and shade on the surface color of objects which light enables us to perceive. A review and clarification of his color system reveals a logical correlation between these phenomena and the various scales in his color system. Studying these scales and understanding the concepts they represent can be very helpful to painters who wish to represent in their paintings objects in space and light in a naturalistic manner.