This article proposes a new gamut-mapping algorithm (GMA) that utilizes both lightness mapping and multiple anchor points. The proposed lightness mapping minimizes the lightness difference of the maximum chroma between two gamuts and produces the linear tone in bright and dark regions. In the chroma mapping, a separate mapping method that utilizes multiple anchor points with constant slopes plus a fixed anchor point is proposed to maintain the maximum chroma and produce a uniform tonal dynamic range. As a result, the proposed algorithm is able to reproduce high quality images using low-cost color devices.
The preparation methods of hollow silver halide microcrystals have recently been reported in the literature, however the study of their properties and application has not yet appeared. In this article the preparation of hollow cubic Ag[Cl,Br], Ag[I,Cl,Br] and tabular Ag[I,Br] microcrystal emulsions is reported. The relation between structure and property of the hollow cubic and tabular silver halide microcrystal emulsions compared with the solid cubic and tabular silver halide microcrystal emulsions comprising almost the same halide composition was studied by means of EDX, SEM, TEM, development with a diluted developer, chemical and spectral sensitization. The results show that the latent image centers are always formed preferentially around the holes of the hollow cubic and tabular silver halide microcrystals. The hollow microcrystal emulsion has a higher efficiency of latent image formation, higher surface reaction activity, and therefore higher chemical and spectral sensitivities. The advantages of hollow silver halide microcrystals can be ascribed to their unique hole structure.
The introduction of iodide into (111) AgBr platelet crystals is known to induce the formation of structural defects, as well as enhance the photographic response of the resulting AgBrI. The incorporation of iodide, introduced uniformly during crystal growth, has been reported to form internal stacking faults, and more recently dislocation arrays. By using thermal processing to induce structural defects to regrow back into their matrix, it is possible to use this technique to probe specific defect characteristics, often at the microstructure level. In this article, we reported a detailed study of two iodide induced defects in (111) AgBrI crystals, using electron microscopy, to determine their location and structural characteristics, as well as to estimate their enthalpy of activation.
The colloidal stability of silver halide emulsions precipitated in aqueous gelatin media is predominantly electro-steric in nature and is provided by gelatin adsorbed on the silver halide grains. It is believed that gelatin provides adequate colloidal stability for spectrally sensitized silver halide emulsions, where the sensitizing dyes compete with gelatin for the silver halide surface. We have examined the details of the interaction of gelatin with unsensitized and sensitized 3-D AgClI emulsions by evaluating the interfacial potential of the emulsions and their colloidal stability as a function of pH and ionic strength. The interfacial potential of the emulsions has been determined using electrokinetic sonic amplitude (ESA) measurements and the colloidal stability of the emulsions was studied using filterability measurements. The unsensitized and sensitized emulsions do not show any appreciable differences in their electrokinetic properties, while they do exhibit differences in their filterability properties upon pH cycling. It is surmised that gelatin is more easily desorbed from the surface of sensitized emulsions than unsensitized emulsions upon pH cycling, leading to aggregation. Hence, we conclude that the weaker adsorption of gelatin on silver halide emulsions is the root cause of the diminished colloidal stability of spectrally sensitized silver halide emulsions. The results suggest that sensitized silver halide emulsions are more prone to destabilization due to process variations than unsensitized silver halide emulsions.
The investigation of kinetics of recrystallization (Ostwald ripening) of silver bromide microcrystals in gelatin was carried out. A theoretical model of the process of mass transfer between microcrystals during recrystallization was proposed and experimentally confirmed. Change of size of the crystals was monitored by a turbidimetric method. It was established that the rate of recrystallization is inversely proportional to distance between crystals in a gel and directly proportional to solubility of the dispersed phase. It was shown on model systems that the growth rate of large crystals is proportional to difference in size of large and fine crystals. It was also revealed that during recrystallization there is a change in growth rate of large crystals, which is caused most probably by change of habit of these crystals. The experimental approach allows study of the driving force and mechanism of recrystallization processes in more detail.
The structure and properties of a variety of sulfur centers are calculated using an embedded cluster method with the density functional method. Models representing adsorbed silver sulfide molecules and compensated surface and bulk substitutional monomer and dimer sulfide are treated. The molecule Ag4S2 partially incorporated into the surface is calculated to have an electron trapping depth of several tenths of an electron volt and a lowest singlet absorption in the long-wavelength range, both of which are consistent with reported experimental measurements of sensitized surfaces. Substitutional dimeric sulfide units incorporated into the surface or bulk and compensated by interstitial silver ions were not found to trap electrons, but holes could be trapped at this center. The ions at a positive kinks containing substitutional sulfide were found to be displaced upon electron trapping indicating a strong coupling of the electron to the crystal lattice. The energy levels, structure and absorption energies calculated for these and related centers are presented and discussed.
We have shown by use of HRS spectroscopy that AgBr nanoparticles exhibit a first hyperpolarizability comparable to materials under consideration for optical technology applications. The technique enabled us to discover the unexpected quantitative conversion of AgBr into the Ag(TAI) complex on treating AgBr nanoparticles with TAI. This result suggests that TAI may function as a silver halide solvent under photographic conditions, with hitherto unconsidered consequences for grain architectural features of small radius. Results on dye adsorption demonstrate that HRS may be a powerful analytical tool for studying the adsorption of dyes on photographic silver halide grain surfaces. From the spectral dispersion of the HRS signals we can identify resonances with electronic transitions of the dyed and undyed particles. These transitions may also be important in their photophysics.
The changes in the morphology and structure of silver carboxylates during thermal and photochemical decomposition were investigated using TEM, x-ray diffraction, and DTA. Thermal and photochemical decomposition of long chain silver carboxylates were both found to form nano-sized silver particles (3–5 nm). This type of metallic silver formation can be directly attributed to the layered structure of the solid state structure of the [Ag(O2CnH2n−1)]2 dimers in the crystalline lattice. In addition, this type of metallic silver was observed to be influenced by the organic by-products formed, which can hinder the addition of new silver atoms to the growing metal crystallite.
Reduction of sensitometric image parameters of two-layer thermally developed photographic materials, subjected to pre-exposure heating, is connected with the presence of toners in the photolayer. It is shown that incorporating the developing agent in the photolayer and the toners in the protective layer improves sensitometric image parameters of such materials. Mechanisms for the effects are discussed.