US2216004A - Method for varying the gradation of lenticulated color films - Google Patents

Description

Sept. 24, 1940. w F T ET AL I 2,216,004

METHQD FOR VARYING THE GRADATION OF LENTICULATED COLOR FILMS Filed NOV. 24, 1937 L NA |\b Second Sens/fv'zea laye r fiufi/JO/fT I q I Ema/5mm i E I g W In uehfors.

Patented Sept. g4, mo 2,216,004. v

mrrnon roa vsnrme m GRADA'I'ION or mm'icvmrnp COLOR. FILMS Wolfgang Falta, Berlin, Edgar Gretener, Berlin- Siemensstadt, Hans Nengebauer, Berlin-Charlottenbllrs', nd Herbert Staude, Berlin-Tempel- 'hoi.',-Germany, assignors, by mesne assignments, -to Kislyn Corporation, New York, N. Y., a corporation of Delaware Application November 24, 1937, Serial no. 178,194 In Germany November 25, 1936 8Claims.

This invention relates to a method for varying the gradation of lenticulated color films.

The gradation or lenticulated films is a characteristic which determines both the contrast of with which the part colors corresponding to the point of the object are reproduced, this ratio should not be changed by any means if the gradation of the total picture is to be enhanced or lessened. This means that the resolving power the finished image and the color quality of images of the additional image must be somewhat of 5 to be reproduced in colors which are produced the magnitude of the order of a lentieular eleaccording to the lenticular color process. For a ment and that it should not be about three times proper reproduction of the colors it is necessary greater, since otherwise besides the change in that the photographic layer have an emulsion gradation as a whole also a change in gradation 10 whose gamma lies in the neighborhood of unity, affecting the reproduction of colors would occur. 10 whereas in the case of smooth film the gradation The invention may be practiced in different is always so chosen that the resulting gamma is ways, selected ones of which will now be deconsiderably higher, for instance, of the order scribed and which will be better understood by or 1.6 to 2. v reference to the accompanying drawing, in which:

The selection of the resulting gradation when Fig. 1 is a diagrammatic view on a greatly en- 15 taking. pictures on films depends among other larged scale showing a cross-section through a things upon the selection of the object. Thus portion of a lenticulated film and also showing particularly in the case of big closeups a smaller certain curves or graphs which will be referred gradation is employed than is usual for pictures to later;

which represent a greater number of objects Fig. 2 is a diagrammatic view on a greatly en- 20 (long shots). larged scale showing a cross-section oi a diiierent If images are to be produced on lenticulated form of film than appearing in Fig. 1 and illuscolor films and their impression corresponds subtrating a dififerent method. stantially to the gradations usual in smooth films, In both Figs. 1 and2 it will be understood that 5 an emulsion must be employed in which the rethe parts are not necessarily to scale or to prosultant gamma difiers considerably from unity. portion, since certain dimensions may be exag- However, if the best reproduction of color is to gerated for clearness of illustration. be obtained the resultant gamma must lie, as far Referring first to Fig. 1, it will be seen that as possible, in the neighborhood of unity. It has this figure shows a lenticulated film which has hitherto not been possible to fulfill both condibehind the support I and emulsion 2. The film 30 tions with the aid of a single emulsion, so that was exposed in the known manner by the use oi. in the case of the projection of lenticulated films a three band colored filter and developed a a omp omis ad to be ad pted tw n th cording to the reversal method. In this case the reproduction of color and the total gradation. emulsion has a transparency which varies as According to the invention the development shown, for instance, by the curve a. Under the 35 and the printing up o he ompletion of th upper three lenticular elements i photographed picture is so e e that the gradation within an object whose color corresponds substantially .very small zones of the l yer is r n from to the color of the central filter band. The transthat which holds good for relatively larger zones. parency of th emulsion is, therefore, greatest To s either Particular devflilopmg procbelow the central band of each lenticular ele- 4o esses are employed or the images, if desired, by t, whereas the transparency of the bands the use of particular layers are intensified or allotted to the lateral bands has 'a small value. reduced in such a manner that the adatmn The ratio of the transparencies of the three part over greater zones is different from that in small hands under each lenticulated element deter zones It is also Possible when Printing by means mines in this case the color of the point of the 45 of a particular printing arrangement to arrange object to Be reproduce that the gradation be influenced in the desired In the embodiment shown in Fig 1 an bj t manneris photographed under the lower lenticular ele- In the method according to the lQVentlon 1t 15 ments, which object has no predominating color 550 essential that the efiect of the addltlonal change and will be reproduced theref r gray or white in gradation be limited to greater Zones than is The values of the transparencies corresponding necessary for the reproduction of colors. Since t th th filter b nd ar th fo approxj the quality of color in the lenticulated color" mately equal (curve b). It is to be noted that process depends upon the values of brightness in the case of white objects a perfectly homogeneous variation of the transparency results 55 only if no straight boundaries are present between the single filter bands in the objective for taking pictures and if the dimensions of the device for producing the lenticulation are also so chosen that no interstices exist between the images of the colored filter in the emulsion. However, in the case of straight boundaries the transparency varies according to the curve I) as shown in Fig. 1.

Furthermore, the average values c and d of the transparency corresponding to the single points of the object without considering the color are plotted in Fig. 1. Therefore, the transparency Tl will differ from the transparency T2, the ratio of these two transparencies indicating the diiierence in brightness between the corresponding points of the object. This ratio determines, however, at the same time the contrast of the entire image so that this ratio must be variable without varying simultaneously the values individually indicated by the curves a and b.

Consequently, a method according to the present invention consists in treating the film after the development. with a potassium blchromate solution in the dark room and then exposing it to the light from the side on which the film is lenticulated. In this case a chromate image is additionally produced in the emulsion, which image is bright at the points at which the film has a small transparency. This chromate image is now converted into a swelling plastic by swelling the whole film in water in the known manner. The film is then treated with a staining solution which is absorbed by the swollen points of the emulsion but is repelled by the points of the emulsion which are not swollen. To this end, for instance, pinatype yellow is employed. in this manner the negative originally present as chromate image is converted into a positive image which presents, however, far less details than the original blackening owing to the small resolving power of the gelatin capable of swelling. P'articularly, the image produced by coloring reproduces no longer the differences in brightness below each lenticular element but only the total gradation of the image. This variation of transparency t isindicated by the curve e. A similar method may be practiced with the use of a suitable ferric salt.

If the original treated as above described is printed in the usual manner, not only the variation of transparency. of the blackening but also the variation of transparency of the colored picture is transmitted to the copy. Since the colored picture represents only diflerences within ranges of the size of the lenticular elements, only the gradation as a. whole is increased in this manner, whereas the reproduction proper of color is not influenced. By a suitable selection of the staining solution, particularly of the density or of the color thereof, the total gradation may be influenced to a large extent.

It is to be noted that the variation of the gradation in the case of the above-described treatment of the original does not remain fixed as such but when printing it may be modified within certain limits by employing colored light instead of white light. If, for instance, the color of the light coincides with the color with which the film has been treated, the variation of the gradation will be only relatively small, whereas when employing a printing light whose natural color is a complementary color to that of the dye a considerably stronger influence of the total gradation will result.

The intensifying process just described utilized the capability of swelling of the emulsion layer. In this case it must be taken into consideration that during the normal treatment of 'a reversal film baths are, as a rule. employed which exert a hardening action on the gelatin. I1 such films are to be treated according to the novel method, the hardening must be eliminated. This may be accomplished in a known manner by employing a potassium bromide solution and a subsequent washing of the film.

Furthermore, it is advantageous to increase the sensitivity of the bichromate process in the known manner by employing suitable sensitizers so as to accelerate the intensifying process. To this end, for instance, lanthanum chloride is suitable.

In the above described intensifying process the emulsion of the picture is used as a support for the additional image which varies the gradation as a whole. In this manner difliculties arise which aggravate the execution of the process or which render it entirely impossible, for instance, if the hardening of the original picture cannot be annulled to a sumcient extent. The method according to the invention may, therefore, be carried out in such a manner that when the original is completed, an additional layer is applied to the film, this layer serving as a support for the picture varying the gradation. If, forinstance, a gelatin layer treated with a chromate solution is employed, the image tobe intensified is iurther treated in exactly the same manner as is the case in the above-described embodiment of the invention.

Also a silver halide gelatin emulsion may be employed as a layer to be subsequently applied, the grains of the emulsion having such a size that the resolving power suffices no longer to separate the ranges corresponding to the single part colors. In this case such an emulsion is rendered capable of being developed by exposing the film from the side on which the film is lenticulated, in which case the gradation of the image may be varied to a great extent by effecting the development in a corresponding manner. Particularly, it is possible to enhance the gradation of the total image by treating the additionally applied emulsion according to the reversal process so that a positive image is produced relatively to the original. However, it is also possible to use only a negative process so that the gradation is reduced by the negative image present on the additional layer. Such a film provided with a coating is shown in Fig. 2. I denotes the support for the coating, 2 is the emulsion proper and 3 the layer subsequently applied which varies the gradation to a great extent. It is preferable to employ in this layer an emulsion which presents as flat as possible a gamma, for instance, about 0.3 to 0.4

A particularly preferred embodiment consists in the fact that when photographing or printing such scenes in which the gradation of the image should be greater than that of the colors, a film is employed which already contains both layers 2 and 3, the layer 2 having a greater resolving power and 3 a smaller.

In some films the emulsion is besides pro-' vided with a protective layer of gelatin which is to prevent the completed image from being scratched and which has been applied particularly for the method according to the invention. For such films it is preferable to efiect the bichromate process in this protective layer so that the emulsion proper does not come into contact with the color. Furthermore, the advantage is obtained in that the entire blackening available in the original layer is employed for the formation of the additional image, whereas when the emulsion swells up an image is produced which is influenced by the distribution of the silver in differently deep layers of the emulsion. This means that those portions of the layer which lie closer to the support are only varied by the light which penetrated the silver lying in front of the portions in the direction of the light. Since in the case of the reversal process the greater part of the silver is distributed over the outer side of the film, falsifications of gradation may thereby occur within the image.

It is essential to the additional image which varies the gradation as a whole that the resolving power be smaller than that of the emulsion proper of the color film. To attain this small resolving power even if the emulsion presents a better resolving power per se, it is advantageous to effect the additional exposure with a very great aperture. Since the photographic layer always tance is of the order of a filter component image itis possible to fade the structure of the original image to such an extent by the light coming from different directions that only the gradation is transmitted as a whole.

Another method for carrying out the invention consists in employing two separate developing processes for the original or the printing film, one of which processes creates a small silver grain and the other a coarse silver grain. For instance, the film may be substantially developed with the aid of paraphenylenediamine and then be subjected to a short subsequent development,

in the case of which, owing to the production of a coarse grain, a corresponding small resolving power is present.

-In general, it is advantageous to subject a film of which prints have been made to the method according to the invention in order to simplify the method. If, however, for instance, only a few' prints are to obtain the varied gradation, it is also advantageous to effect the printing process in such a manner that besides the recording corresponding to the colors also an image is produced which substantially corresponds to the change in gradation. This may be accomplished, for instance, by arranging behind the printing film a surface which directs the light passing through the film once more to the emulsion so that the zones corresponding to the single component colors cannot be clearly distinguished from one another. To this end, for instance, a slightly roughened reflecting pressure plate in the film gate is sufiicient. By varying the reflecting power of this plate it is possible to obtain a more or less great change in gradation as a whole with a constant gradation in details.

We claimr 1. In color photography, the method which comprises forming an image of an object in the sensitized layer of a lenticulated film, said image comprising a group of color records behind each lenticulation, the sum of colors of the filters used to produce the records in each group giving substantially the efiect of white light, and then forming in register on the image therein a supplementary duplicate image, the resolving power of which has a magnitude which is of the order of that of one of said lenticulations.

2. In color photography, the method which comprises forming on an image in the sensitized layer oi an exposed lenticulated film a supple mentary duplicate image, the resolving power of which has a magnitude which is of the order of one lenticulatio'n.

3. In color photography, the method which comprises forming an image of an object in the sensitized layer of a lenticulated film, said image comprising a plurality of groups of color records, the sum or .the colors. or the filters used to produce the records in each group giving substantially the efiect of. white light,- treating the film with a sensitizing agent which on exposure to light renders the resensitized layer differentially absorbent to dye solutions, exposing said image to light through the film base, swelling the unexposed portions 01' the resensitized layer, and then treating with a staining solution of a character which will be differentially absorbed by the swollen parts of the sensitized layer,

4. In color photography, the method which comprises forming an image of an object in the sensitized layer of a lenticulated film, said image comprising a plurality of groups 01' color records, the sum of the colors of the filters used to produce the records in each group giving substantially the 'efi'ect of white light, treating said layer with chromic salts, exposing to light pass.- ing through the film base, and staining'with a material which is diflerentially absorbed by parts oi! the layer swollen by said salts.

5. In color photography, the method which comprises forming an image of an object in the sensitized layer of a lenticulated film, said image comprising a plurality of groups of .color records, the sum of the colors or the filters used to produce the records in each groupv giving substantially the efl'ect of white light, treating saidi layer with potassium bichromate, exposing to light passing through the film base, and staining with a material which is diflerentially absorbed by parts of the layer swollen by said p0- tassiurn bichromate.

6. In color photography, the method which comprises forming an image of an object in the sensitized layer of a lenticulated film, said image comprising a plurality of groups of color records, the sum of the colors of the filters used to produce the records in each group giving sub stantially the eflect of white light, then forming on the image therein a supplementary duplicate image, the resolving power of which has a magnitude which is of the order of a lenticulation, and printing from said film with colored light.

'I. In color photography, the method which comprises forming an image of an object in the sensitized layer of a lenticulated film, said image comprising a plurality of groups of color records, the sum of the colors of the filters used to produce the records in each group giving substantially the eflect of white light, treating the mm with a sensitizing agent which on exposure to light renders the resensitized layer difierentially absorbent to dye solutions, exposing said image to light through the film base and through a lens having a relatively large aperture, swelling the unexposed portions of the resensitized layer, and then treating with a staining solution of a character which will be differentially rial which is differentially absorbedby parts of the layer swollen by said salts.

' WOLFGANG FALTA.

EDGAR GRETENER. HANS NEUGEBAUER. BIB-BERT BTAUDE.

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