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2 2012

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Reconstruction of silver halide volume reflection holograms at the wavelengths of recording

Ivanov B., Shopova M., Stoykova E., Sainov V.

Optica Applicata

2012

Vol. 42, nr 3

643-650

Reconstruction at the wavelengths of recording is obligatory in color holography. If recording is made on silver halide light sensitive materials, a shrinkage of the layers causes different shifts of diffraction peaks towards lower wavelengths. The shrinkage is compensated by suitable swelling before final drying of the holograms. The report presents recent results obtained for swelling of holograms recorded at wavelengths in the red, green and blue spectral regions for an ultra-fine grain panchromatic silver halide emulsion with 10 nm average size of initial silver halide grains. The cases of successive and simultaneous irradiation of a single silver halide plate with the three wavelengths used are compared. Experiments on repeatability of the swelling procedure are also provided. Diffraction efficiency of bleached single exposure volume reflection holograms in red, green and blue has values higher than 50% for exposure energy of 2.0 mW/cm2 both for the CW and pulse lasers.

Investigation of color inconstancy and color gamut changes of printed images depending on the standard illuminants

Spiridonov I., Shopova M., Boeva-Spiridonova R.

Optica Applicata

2012

Vol. 42, nr 3

627-641

The main goals of this research are investigation and determination of color balance failure (color inconstancy) of offset printed images expressed by color difference depending on the material used and different standard illuminant conditions. For the experiment, we chose three of the most commonly used in practice illuminants - CIE D50 natural horizon daylight with color temperature 5003 K; CIE F2 cool white fluorescent, 4230 K; CIE A typical Tungsten-filament lighting, 2856 K. A special test form that has been used contains different control strips and measurement components include test chart TC6.02 with about 1000 color patches with different percent combinations of cyan, magenta, yellow and black. The paper, printing inks and printing presses employed in the experiment are some of most commonly used in practice for producing high quality color reproductions. A series of colorimetric and densitometric measurements were performed for different combinations of C, M, Y, K in single, double, triple and quadruple overprint for high tones, middle tones and dark tones. For estimating color balance failure for all the above mentioned measurements there have been calculated the color difference ?E*ab and CMCCON02 depending on standard illuminants CIE D50, F2 and A. For the first time via experimental research in real production conditions (for offset printing method), 3D and 2D presentations and comparison of color gamuts and color gamut volumes for different illuminants were made. According to the results, CIE A has the biggest color gamut volume and CIE F2 - the smallest one. The results obtained are important from scientific and practical points of view. For the first time a methodology is suggested and implemented for examination and estimation of color shifts by studying a big number of color changes in various ink combinations for different illuminants.