A spectral model was derived to predict the spectral reflectance factor of colors formed using a color proofing system simulating offset printing. A first-order model was based on the spectral Neugebauer equation modified by the Yule-Nielsen correction in which n was assumed to vary as a function of wavelength. The nλ and effective dot areas were optimized using primary (cyan, magenta, yellow, and black) halftone tints. Systematic errors were observed. The systematic error behaved in a similar fashion to the phenomenon of ink trapping. Because ink trapping, ink spread, ink mixture and variance of mechanical dot gain were negligible for this proofing system, this is an optical effect to be referred to as “optical trapping.” An interaction model was derived that compensated for optical trapping. Adding the optical trapping effect to the first-order model significantly improved model prediction to an average ΔE*ab, of 2.2 with a maximum of 5.5. A simple black printer model was derived for an inversion of the forward model that aimed to provide a similar black amount with a conventional color-separation method and colorimetric match applying a concept of under-color removal (UCR) in original density space with tone reproduction curves of a gray scale. Using the Simplex method, the modified spectral Neugebauer model with the black printer model was inverted to build a backward model. Influences of the dot area transform function obtained from the backward model were compared with those from a conventional method for an evaluation of similarity. A desktop drum scanner was colorimetrically characterized using a spectral reconstruction model for a reflective photographic material to build a concatenated device profile in which digital counts of a scanned photographic reflection print were the input and those of the roofing system were the output. Performances of the concatenated device profile were evaluated for practical use. The average ΔE*aberror from the profile was 2.1 including colors outside of the proofing system's color gamut.
In this article, we evaluate the qualities of images obtained by the multi-level error diffusion method and propose objective parameters for evaluation of image quality. The results of the subjective evaluation experiments show that the image quality is improved as the number of output levels increase, but the improvement is saturated at 8 levels in 400 dpi resolution and 24 levels in 200 dpi. The objective parameters proposed in this study are rms (root mean square) granularity and SNR (signal to noise ratio). The results of the subjective evaluation show that these parameters are useful to evaluate the quality of the images obtained by the multi-level error diffusion method.
The effects of receiver stock and platen covering on pressure in a thermal printer nip were investigated using the nonlinear finite element method. “Design of experiment” techniques were used to reduce computational effort. Pressure in the nip is shown to be dominated by receiver thickness and stiffness. Examples of pressure versus head load are given and the relationship between these important variables discussed.
The scope of this study was to correlate the topographic information provided by atomic force microscopy (AFM) with optical properties of the AgX tabular grain photographic emulsion samples collected with near-field optical microscopies. Images of spectrally sensitized AgBr tabular grains were performed, using both AFM and photon scanning tunneling microscopy (PSTM). PSTM images of spectrally sensitized AgBr microcrystals, recorded at various excitation wavelengths, showed an amplification of the apparent thickness of the grains when excited in the absorption range of the dye. This can be explained by the contribution of the fluorescence of the sensitizing dye to the measured signal in the PSTM. The increase of the PSTM response depended also on the dye coverage and on the stack of microcrystals. The visible absorption and fluorescence spectra of the spectrally sensitized emulsion obtained at room temperature at a macroscopic scale were in good agreement with the PSTM observations.
In the previous work, the present author proposed a comprehensive model for sulfur sensitization according to which monomers and dimers of substitutional sulfide ions on silver halides are sulfur sensitization centers acting as positive hole traps and electron traps, respectively, while silver sulfide clusters are fog centers. The model was supported by characterizing those centers on octahedral and cubic silver bromide emulsion grains with equivalent circular diameter of 0.2 μm. The difference in oxidation potential and absorption spectrum between sulfur sensitization centers and fog centers was distinctive enough to be ascribed not merely to the difference in size, but also to the difference in the state of the sulfide ions. As many as 500 silver sulfide clusters (i.e, fog centers)/grain (i.e, 2400/μm2) were observed by an electron microscope in slightly fogged emulsions, indicating that the developability of each cluster was very low. The above concentration of fog centers was independent of the amount of silver sulfide formed among variously fogged emulsions, suggesting that sulfur sensitization centers as well as fog centers were formed at surface sites, where sulfide ions were stable and liable to be coagulated. The belief is that low developability of silver sulfide clusters makes it possible to achieve high sensitivity and stability without fog formation in sulfur-sensitized emulsions.
The effects of different substituents on thiacarbocyanine and indocarbocyanine dyes on their adsorption to AgBr microcrystals and on size distributions of J-aggregates were investigated by analytical color fluorescence electron microscopy (ACFEM). The results showed that the adsorbability of the indocarbocyanine iodide dye on cubic AgBr grains was greater than that on the T-grain AgBr. On the other hand, adsorbability of the thiacarbocyanine triethyl ammonium salt on the T-grain AgBr was greater than on the cubic AgBr. In addition, adsorbabilities of 5-substituted thiacarbocyanine dyes either on T-grain or on cubic AgBr were much greater than those of 5- unsubstituted thiacarbocyanine dyes. We inferred that growth of J-aggregates on AgBr could be egarded as Ostwald ripening, and that substitution of the indocarbocyanine with an N-ethyl substituent led to strong J-aggregation. The average size of J-aggregates of 5-substituted thiacarbocyanine dyes formed on cubic AgBr were larger than the average size of J-aggregates of the 5-unsubstituted.
An accelerated test for the oxidative discoloration of developed silver images has been studied. While hydrogen peroxide testing has been used to predict the oxidative discoloration of developed silver images in monochrome photographic materials, this method is sometimes impractical when applied to materials stored under a “normal atmosphere” in which the contents of aggressive oxidizing chemicals are small or nonexistant. The article presents a new testing method that uses incubation in an atmosphere of compressed oxygen to accelerate oxidative discoloration. Such incubation for one or two months was found to reproduce the oxidative discoloration occurring in radiographic films stored under a normal atmosphere for four or five years under the climatic conditions of the Tokyo area. And an induction period in which discoloration is imperceptible was observed in the blue density increase of this accelerated testing. From these results, the mechanism of the oxidative discoloration is discussed and the rate-determining process of this discoloration reaction is presumed to be ion migration in the gelatin layer.
Thermal yellowing refers to the dark-keeping increase of blue density in Dmin and low/mid density areas of color negative and reversal prints such as that which occurs with album storage of prints. Arrhenius testing is normally used to predict the time to reach a specified amount of yellowing. Recently generated data show that not only the rate of stain but also the maximum amount of stain, is temperature dependent. At 20°C the maximum stain for a typical color negative paper is predicted to be 0.09 Status A blue Dmin increase.