Gevacolor Print Film T 9 85
Subtractive 3 color: Chromogenic monopack
(Agfa-Gevaert N. V.)
Original Technical Papers and Primary Sources
Verbrugghe, R. G. L.; Seys, W. A.; Eynard, R. A. (1971): A New Color-Print Film for Universal Applications in Color Printing and Processing Systems. In: Journal of the Society of Motion Picture and Television Engineers, 80,7, pp. 559–563.
“A New Color-Print Film for Universal Applications in Color Printing and Processing Systems
By R. G. L. Verbrugghe, W. A. Seys and R. A. Eynard
Gevacolor Print Film, Type 9.85, is a conventionally designed color positive film with each of the three light-sensitive layers containing an appropriate dye coupler. Exceptional sharpness and excellent color saturation, achieved by very stringent selection of the various dye couplers, combined with extremely thin emulsion layers make the film especially suitable for small formats. Processing is based on a commercially available color developer which uses 2-amino-5-diethylaminotoluene monohydrochloride. This film can be processed together with other similar color print films using exactly the same processing methods, solutions and processing times without causing any contamination whatsoever.
In the past dozen years, many types of color positive films have been put on the world market by several film manufacturers. The diversity of these films has made it necessary for the film laboratories practically to install one processor for each different film type. This has hindered those labs which preferred selecting film from various supply sources, forcing them to standardize their color operations. These problems were many years ago eliminated for black-and-white motion pictures, where similar film types of different manufacturers can be processed simultaneously using the same processing machines and solutions. Now this can be done in color as well.
Agfa-Gevaert has been striving to achieve uniformity in processing and printing of color positive film. A color positive film should be considered as a mass film product, having wide applications in the field of mass-communications systems, from 70mm to 8mm film formats. Every film processing laboratory the world over needs an operation for color positive film. With this aim, a conference was cosponsored in September 1961 in Paris, during which several film manufacturers discussed the possibility of standardizing the processing of color positive film. Agfa-Gevaert, striving for as simplified a process as possible, introduced shortly after the conference Gevacolor Positive Film, Type 9.53, followed by Gevacolor Positive Film, Type 9.54.
Afga-Gevaert’s new print film, Type 9.85, has a process based on a color developer which uses 2-amino-5-diethylaminotolucne monohydrochloride, commercially available under the trade name of CD-2, Color Agent B, and Code 2 as a Developing Agent. Type 9.85 can be processed together with other similar color print films using exactly the same processing methods, machines, solutions and processing times without causing any contamination whatsoever to the other films. Furthermore, exceptional sharpness, high sensitivity and excellent color saturation are achieved. This was accomplished by a very stringent selection of the various dye couplers, combined with very thin emulsion layers, making T. 9.85 suitable for all applications, especially for small-format films.
Gevacolor Print Film, Type 9.85, is a multilayer film for printing color release prints from color negatives, with or without a mask or from any color duplicating stock. The film basically consists of three separate emulsion layers coated on a safety base. These layers are sensitive to green, red and blue light, respectively. They contain appropriate color couplers, which will produce, respectively, a magenta, a cyan and a yellow dye image during development.
A protective gelatin overcoat is coated on top of the emulsion and a black antihalation layer is coated on the base of the film, which like most commercial color positive films consists of a removable resin, containing carbon black (Fig.1).
Although the film structure is generally similar to other commercial positive films as far as the position of the layers is concerned, interlayers have not been provided between the emulsion layers. This was found unnecessary since no color contamination by interaction between emulsion layers occurs, partly as the result of the characteristics of the color couplers selected, and partly the result of the gelatin-silver halide color coupler ratio in the layers themselves. The thickness of the green sensitive emulsion layer is only 4.2 μm; therefore this upper layer shows a remarkable improvement in the general sharpness characteristics of this new film material.
One of the most important photographic requirements in the manufacture of a color print material is the form of the sensitometric curve in terms of equivalent neutral densities. With T. 9.85, the form, e.g., the slope, the toe and the straight line portion of the sensitometric curve have not only been directed by the system analysis, but also by the urge to work out a universal type of positive print film; hence the sensitometric characteristics of color print materials of other manufacturers were thoroughly studied, leading to the general shape of Fig. 2. Care was taken to stick to the gray standard and henceforth no special changes in the slopes of the H&D curves were allowed. This was done because the best general color rendition results from respecting the “gray standard” condition. Improvements in the rendition of colors have to be achieved mostly by careful selection of color couplers.
The photographic color image of Gevacolor Print Film, Type 9.85, is formed by a subtractive mixture of yellow, magenta and cyan dyes. The proportional quantities of these dyes were selected in such a way that the color image, subtractively formed, if projected with a xenon light source, matches the visual perception of a gray scale.
The quantities of the individual dyes required to produce gray are determined by the spectral characteristics of the dyes, the energy distribution of the light source and the spectral sensitivity of the eye of the observer.
When determining the sensitometric characteristics of the green-sensitive layer, which primarily decides the tonal scale of photographic reproduction, the characteristics of the blue- and red-sensitive layers are determined at the same time, because the gray balance presumes a fixed relationship between the quantities of dyes.
In Fig. 3 the spectral density of the quantities of the cyan, magenta and yellow dyes are shown and form a metameric match for a neutral gray of density 1.00 (10% transmission) by subtractive mixture and a xenon illuminant. The spectral density of nonselective gray is shown for a density 1.00 by the dotted line.
A densitometer with an accurately known spectral sensitivity is used for measuring the sensitometric characteristics of a photographic color material. This spectral sensitivity is determined by the spectral sensitivity of the sensor (e.g., a photomultiplier) and by the spectral characteristic filters used for measuring densities.
Figure 4 shows the spectral sensitivity of a densitometer with Status A filters and a sensor with an S9 photomultiplier tube characteristic.
During the measurement of the sensitometric characteristics, the measuring instrument integrates the light quantity reaching the sensor through the strip of film under measurement. This means that the results are determined by the spectral sensitivity of the measuring instrument used.
Figure 5 shows the results of a strip of Gevacolor Print Film, Type 9.85, which is visually gray over the entire density range, and which is measured on a Macbeth TD 203 Densitometer equipped with Status A filters. This gray can be obtained by exposing a strip of film through a gray wedge and a filter having the same spectral characteristics as the maximum mask of the negative film, as well as a set of color correction filters in order to adjust the sensitivity of the three layers. In spite of the fact that the three curves of Fig. 5 (blue, green and red filter measurements) do not coincide, and the red filter measurement gives the greatest deviation, the test wedge on which the measurement was carried out shows a perfect gray. Any deviation from this sensitometric condition may indicate a disturbance of the gray color balance.
In Fig. 6, integral density versus log E curves are given, according to measurements made with the Joyce-Gevaert Densograph for T. 9.85 processed after an exposure, giving visual gray. The speed of the three emulsion layers has been fixed so that printing with any commercial available printers, either additive or subtractive contact or optical does not cause any practical problems, and that minimum corrections with, e.g., CC filters are needed when prints are to be made from masked color negatives or intermediates.
Spectral Sensitivity (Darkroom Sensitivities)
Figure 7 shows the spectral sensitivity curves of Gevacolor Print Film, Type 9.85. Minimum sensitivity between the green and red regions of the spectrum, 5700 to 5900 Å, enables printing and processing under conventional safelights, e.g., by direct illumination with a sodium vapor lamp at a distance of 2.5 ft. Agfa-Gevaert Safelight Filters 08 or 09 can be used.
Spectral Density Curves
The color couplers were so selected that an optimum result was aimed at obtaining an excellent color rendition, a good dye stability after processing and a pleasing color image, among others (Fig. 8).
A careful selection of emulsion characteristics such as AgX/gel ratio, emulsion thickness and grain dispersion, in order to minimize the light diffusion and reflection in multilayer materials, give T. 9.85 an excellent definition. Furthermore, in some of the layers color couplers were used which yield a very narrow color spread function after color development. Sharpening dyes were also added to the emulsion layers. The spectrometric curve of the sharpening dyes was so computed that a maximum gain in sharpness with a minimum loss in total sensitivity was obtained, whereas the relative sensitivity has been so defined that a minimum correction is needed while printing from masked originals or duplicates. Figure 9 shows the MTF (modulation transfer function) curves of T. 9.85 that have been computed from readings of images of sinusoidal targets, which have been printed to a neutral gray. The measurements were made selectively, using Agfa-Gevaert red, green and blue selection filters. The sharpness of the material, especially the MTF curve of the green sensitive or top layer, might need some further comments. In Fig. 10 the MTF curves of the typical black-and-white motion-picture films of different makes are compared with those of T. 9.85. Knowing that about 60% of the total image quality in a color film is determined by the image magenta dye, one can easily presume that the image quality of the T. 9.85 prevails over the normal black-and-white print film quality. Hence T. 9.85 is also especially suited for the smaller film sizes, including the super 8.
One of the reasons for the excellent sharpness characteristics of the new color print film is the “color spread function” of the diffusable dye formed during color development.
In Fig. 11 the modulation transfer of the color coupling process is given for the magenta, cyan and yellow color coupler. For this purpose T. 9.85 has been processed in a normal black-and-white developer to give only the effects of optical spread function. Selective exposures were made, using blue, green and red narrowband filters. Black-and-white development was compared to color development.*
Figure 11 clearly shows that practically no image spread occurs due to color forming in the green sensitive layer, up to 100 lines/mm. The fact that the response exceeds 100% is due to the relief effects in the upper layer. The cyan dye reveals a minor loss. The yellow dye formed in the blue-sensitive layer accounts for only 15% of the image quality and has a minor (lower) response in the high frequencies. The resolving power for a test object with a contrast of 1000:1 amounts to 270 lines/mm.
The granularity of a print depends upon a lot of factors combined such as the granularity of the negative (or duplicates), the MTFs of the negative and positive materials used including the printing step and upon the granularity of the print film. Although the granularity of the positive has the minor part in the equation, it might be of some interest to evaluate or compare some figures in terms of rms values. The rms value of the T. 9.85 for a density of 0.8 above fog level was found to be 0.011; the scanning was performed by a circular spot of 25-μm diameter with the optics having a numerical aperture of 0.25.
In Fig. 12 the color rendering of the T. 9.85 print film of a restricted number of color patches is given in a CIE chromaticity diagram; the color rendering of the different colors is compared with three other color print films available in the USA. The results given are based on computations with the IBM 1800, where the photographic process is simulated in all of its steps; care was taken to evaluate each of the materials in the calculated sensitometric conditions for neutral equivalency.
In Table I the statistical weighed color deviation between original and reproduction is given, calculated and expressed in terms of the 1964 CIE color difference formula; the original contains 43 colored patches and 13 gray patches. The patches are grouped in the different color groups, and include flesh (Fl), foliage (Fo), sky (S), red (R), green (G), blue (B), yellow (Y), cyan (C) and magenta (M).
The results indicate that the T. 9.85 enables good reproduction of the colors having great importance: flesh, foliage, sky blue and red. The relatively great deviation for green, which occurs for all of the print films, is due to a loss of brightness, rather than to a loss of color saturation.
For optimum reproduction, it is advisable that the printing of the soundtrack be confined to the upper two layers. This can be achieved by any selective yellow filter; after bleaching, the rehalogenated silver of the top layers is redeveloped by selective application of a very active black-and-white viscous soundtrack developer.
In Fig. 13 the relation between density of the negative and density of the positive is given in order to obtain optimum cancellation. These printing conditions are simply to be considered as a guide. In Fig. 14 the frequency characteristic is given for a print of a soundtrack 16mm variable area on the color print film T. 9.85.
In recent years more and more importance has been given on good dye stability, even in the fields where dye stability seemed to be less important. Therefore special care was taken regarding the choice of color couplers, in connection with their dye-keeping qualities.
In Fig. 15 the integral density versus log exposure characteristics are given for neutral strip of T. 9.85 measured after accelerated dye fading tests, and compared to the measurements of the same strip, before undergoing these tests. Figure 15 refers to the test conditions as prescribed by the test condition B, USA Standard Institute; temperature 140 ± 1°F, and 70 ± 2% of relative humidity with a time lapse of one week. This condition is referred to as being favorable in simulating results which occur after long term storage.
Although the validity of the accelerated dye fading test is not challenged, we consider that humidity should show less practical influence on the dye stability when considering the specific use of motion-picture projection material; dry heat can be far more relevant for motion pictures kept in cans.
From Fig. 15 it can be seen that the keeping of dyes is very good; very little shift occurs, which practically does not affect the gray balance. Special attention is drawn to the fact that the magenta dye needs the normal stabilization by formaldehyde stabilizing bath.
A sodium-vapor light source with an Agfa-Gevaert 09 safelight filter to reduce the unwanted wavelengths is best suited for darkroom illumination in the printing-and-processing rooms. Also acceptable is a 15-W bulb used with an Agfa-Gevaert filter 08 or a Wratten series 8.
Gevacolor Print Film, Type 9.85 specially has been designed to be fully compatible with existing and known processing systems in the U.S. This applies to exactly the same solutions, processing times and various temperatures, i.e., 70°F up to 75°F as recommended in earlier issues of the Journal of the SMPTE. The color developing agent 2-amino-5-diethylaminotoluene monohydrochloride, a commercially available chemical, is being used in the color developer. As a rule 75°F should be considered as the standard processing temperature. The sensitometry of T. 9.85 is not greatly influenced by developing time variations, and the film maintains its given color balance very well. The same also applies to tolerable deviations in the concentrations of the most important chemical ingredients of the color developer, such as the developing agent, potassium bromide, sodium carbonate, sodium sulfite, as well as generally accepted variations of total alkalinity and pH values.
Extensive use of this film in European countries has shown that T. 9.85 does not cause any contamination whatsoever to the color developer or any of the secondary baths and that the sensitometric characteristics of competitive color print materials processed in the same developer remain unaffected. Finally the swelling characteristics of T. 9.85 in the color developer should not lead to different replenishing rates; normal replenishing procedures thus far applied can remain unchanged.
The rawstock Gevacolor Print Film, Type 9.85, should be stored at a maximum temperature of 10°C or 50°F or preferably lower, in case a longer storage period can be anticipated, and at a relative humidity of 50%. Upon removal from storage, sufficient time should be allowed for the film to reach room temperature, before removing the tape from the can. Exposed film should be processed as soon as possible.
* R. Verbrugghe, M. De Belder and G. Langner, “Influence of the color coupling process on granularity and sharpness in color flints,” SPSE, 11: 379–384, Nov./Dec. 1967.
Presented on April 27, 1970, at the Society’s Technical Conference in Chicago by R. G. L. Verbrugghe and W. A. Seys, (who read the paper), Agfa-Gevaert N.V., 2510-Mortsel (Antwerp), Belgium, and R. A. Eynard, Agfa-Gevaert Inc., 275 North St., Teterboro, NJ 07608.
(This paper was received on October 20, 1970.)”
(Verbrugghe, R. G. L.; Seys, W. A.; Eynard, R. A. (1971): A New Color-Print Film for Universal Applications in Color Printing and Processing Systems. In: Journal of the Society of Motion Picture and Television Engineers, 80,7, pp. 559–563.)