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Characteristic curves of colour pho-tographic materials are measured with red, green, and blue filters so as to evaluate their three differently sensitized layers by means of three curves. When pictures are projected in dark surrounds, their apparent contrast is reduced, so that their objective contrast has to be raised to produce pictures of apparently correct contrast. Characteristic curves of colour materials intended for projection in dark surrounds enable this increase in contrast to be measured and controlled. The cyan, magenta, and yellow dyes used to form images in colour materials have unwanted absorp-tions in parts of the spectrum outside their main absorption bands; these unwanted absorptions are corrected by the use of coloured couplers and inter-image effects; characteristic curves provide indispensable insights into these processes.

Dark stability of the magenta dye image obtained from 2-equivalent 3-acylamino-5-pyrazolone couplers was investigated from the viewpoint of the reaction of the magenta dye with the residual coupler.A correlation was found between the reaction rate and the pKa values of the starting 3acylamino-5-pyrazolone couplers, i.e., the couplers with the lowest pKa values showed the least reactivity. This observation suggests that the reaction proceeds via an ionic reaction mechanism rather than by a radical reaction mechanism.The use of couplers with low pKas for colour negative film makes it possible to remove formaldehyde from the stabilizing bath in colour negative processing.

In order to confirm the fading reaction mechanisms of magenta azomethine dyes in the presence of bisulphite and thiosulphate ions, a faded material was synthesized from viewpoint of organic chemistry. Then identification was made on the compound by means of elemental and spectroscopic analyses. The colourless compound prepared was proven to be an adduct of dye and bisulphite ion hydrated with one molecule of water, and to be identical with the faded product observed in situ by Miyagawa et al according to spectroscopic analysis. Kinetic and thermodynamic parameters of the formation of the colourless compound are also provided in this paper to confirm the above result.

Mordanted azo-naphthol cyan dyes have been shown to be susceptible to attack by atmospheric sulphur dioxide to yield a magenta product. The reaction is catalysed by the presence of water. It is also reversible. The rates of the forward and back reactions are strongly influenced by the structure of the dyes. The reaction involves the addition of HS03- to the naphthalene ring, yielding a 3-sulphonated tetrahydroxynaphtllalene.

A new type of thermally processed chemipholographic imaging element is described In which images are formed by electrical exposures of an electrothermographic Co-C-Fax CET composition comprising a Co(III)-diamine complex, a colour developer, and a colour coupler. Negative cyan, magenta, and yellow images are formed using p-aminophenols and sulphonylhydrazones as developers in combination with conventional Couplers. A cathodic mechanism of latent image formation involving reduction of the Co(III)-diamine complex has been proposed, and colour discrimination based on polarity effects associated with this mechanism has been demonstrated.

The new Polaroid ® instant colour print system, SX-70, uses metallized dyes, cyan, magenta, and yellow, which have superior light fastness properties. Structures for the dye developers are given, and also comparative fading data for the colour prints and a high quality commercial chromogenic colour print material. A further step of improvement has been achieved in another experimental colour print material using the same dyes. In the SX-70 print the processing chemicals remain with the picture.

In colour masking for continuous tone processes, the number of masks which is generally required can be reduced if the unwanted densities of the dyes are suitably related to each other. In particular, in a process employing dyes which have three unwanted densities (the yellow having no densities to red and green light and the magenta no density to red light) the three masks required can in certain cases be reduced to two. A suggestion that a similar simplification might be achieved in the masking procedure for halftone processes outlined in a previous paper is examined, and it is concluded that if the unwanted densities of the inks obey the condition which allows the reduced number of masks in a continuous tone process, then the same number of masks in a halftone process should give results which differ only little from those obtainable with the more correct full number of masks.

The construction of a computational model representing a masked negative film is described. Model negative tripacks are then used in the context of a complete negative-positive system to demonstrate the changes in colour reproduction which result from increasing the degree of masking of the magenta dye.

Practical methods of colour masking developed by the authors in 1948-1958 are described. Reaction of unused colour coupler with diazotized amines and aldehyde-anils proved unattractive due to the need for exact control of the extra processing steps involved. Masking of the cyan dye image was accomplished by reaction with formaldehyde and colour developer followed by oxidation; masking of the magenta dye image was accomplished by the use of styryl dyes and aldehyde-bis-pyrozolone couplers followed by reaction with formaldehyde. The mechanism of these reactions is discussed in the light of chemical and photographic evidence.

The ratio of Coupling Rate Constant: Deamination Rale Constant (k2, k1) for a considerable number of magenta, yellow and cyan developer soluble colour couplers has been determined by competition between deamination and coupling. The determinations were made in a medium approximating to the colour developer using 5-diethylamino-2-aminotoluene as the developing agent. pK measurements showed that all the colour couplers were fully ionised in this medium. The photographic data have been shown to fit the empirical equation, γ = A log t + B where γ = Contrast, t = Time of Development in minutes, A = Activity Constant and B = Inducticn Constant, k2, k1 and A values have been shown to be related by the equations, A=3.55 e–5.05×102(K1/K2) for oxidation by K3Fe(CN)6 A=3.55 e–5.05×102(K1/K2) for oxidation by AgCl.These equations show that the photographic activity of a colour coupler is related to its rate of coupling with oxidised developer and increases with increase in k2/k1. Further they also show that t...

Seventeen substantive yellow, magenta and cyan colour couplers have been characterized by colour coupling activity and photographic activity. Colour coupling activity was measured in terms of the rate constant of coupling k., in units of the rate constant of deamination of the colour developing agent. The measurements were made in a medium approximating to the colour developer using N-ethyl-N-(5-hydroxy-pentyiyp-phenylene diamine acid sulphate as the developing agent and silver chloride as the oxidant. The photographic activity was determined using equimolecular coatings of the colour couplers for a given coating weight of silver halide in negative emulsion. The photographic data fitted the Elvegard equation,γ=A log t + Bwhere γ=Colour Contrast, t=Time of Development in minutes, A=Activity Constant (=tdγdt 1loge) B=^Constant. A and k2, were related by the equation,where α and β are constants of the system used.The presence of oil formers has little effect on k2, as has the micellar state of the co...

A description is given of on enlarger designed for making colour prints. The colour of the light illuminating the negative is continuously variable by means of cyan, magenta, and yellow sliding filters, the light from which is mixed by means of a box of mirrors; the unwanted absorption of one of these filters is compensated for by means of an auxiliary sliding filter. Monitoring for colour balance is carried out by allowing light from the negative to fall on barrier-layer cells covered by red, green, and blue filters; monitoring for density is carried out by means of an unftltered cell at the paper plane; a galvanometer is used to measure the photo-currents. The monitoring system can be used either as a calibration for the sliding filters, or as a means of making prints whose integrated light approximates to grey. A potentiometer net-work provides controls for paper speed and for “plus and minus” correction in both density and colour according to the subject-matter in the negative.

The optimum combinations of cyan, magenta, and yellow dyes in present-day subtractive colour photography have been investigated by means of a computer simulation method. The investigations have been carried out from the viewpoints of the stability of Selective greys against the illumination metamerism and also against the small changes of dye amounts.

A description is given of on enlarger designed for making colour prints. The colour of the light illuminating the negative is continuously variable by means of cyan, magenta, and yellow sliding filters, the light from which is mixed by means of a box of mirrors; the unwanted absorption of one of these filters is compensated for by means of an auxiliary sliding filter. Monitoring for colour balance is carried out by allowing light from the negative to fall on barrier-layer cells covered by red, green, and blue filters; monitoring for density is carried out by means of an unftltered cell at the paper plane; a galvanometer is used to measure the photo-currents. The monitoring system can be used either as a calibration for the sliding filters, or as a means of making prints whose integrated light approximates to grey. A potentiometer net-work provides controls for paper speed and for “plus and minus” correction in both density and colour according to the subject-matter in the negative.