US2751294A

US2751294A - Photographic method of obtaining a film transparency

Info

Publication number: US2751294A
Application number: US479432A
Authority: US
Inventors: George L Morrison
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-01-03
Filing date: 1955-01-03
Publication date: 1956-06-19
Anticipated expiration: 1973-06-19

Description

June 19, 1956 G. MORRISON 2,751,294

PHOTOGRAPHIC METHOD OF OBTAINING A FILM TRANSPARENCY Filed Jan. 3, 1955 2 Sheets-Sheet l INVEN TOR.

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United States Patent PHOTOGRAPHIC METHOD OF OBTAINING A FILM TRANSPARENCY George L. Morrison, Evanston, Ill.

Application January 3, 1955, Serial No. 479,432

12 Claims. (Cl. 95-5) The present invention relates generally to the graphic arts and more particularly to a method of obtaining a film transparency having a plurality of images arranged into a montage formed therein from printing elements which have relief printing surfaces and initial film transparencies having images formed therein, the derived transparency being subsequently usable in forming a plate for a printing press.

In the everyday production of certain types of lithographic printing surfaces, for example, in the practice of the albumen and deep-etch offset processes, the text and other material to be reproduced are transferred to a plate which may be used in a printing press by a process which requires the use of a photographically reproduced print or transparency of the material to be reproduced. The photographic transparency used is either a positive or a negative, depending upon the process employed in making the plate for the printing press. An involved and time consuming procedure has generally been required to obtain a transparency which includes both half-tone and line work. It has been the practice to make separate transparencies of the half-tone work and of the line work and then assemble these transparencies together by stripping. The term stripping in the graphic arts is used to denote the proper assembly upon a layout of all of the transparencies or film units into the final printing form. After the stripping operation, certain areas, such as for example, the areas between the margins of the various transparencies, are darkened in an operation usually referred to as masking and/ or opaquing. Finally, the stripped, masked, and opaqued film assembly is used as is, or is photoprinted to form a suitable composite transparency which is used in the subsequent process of forming the final press plate.

The usual manner of forming the initial transparency of the line work has been to set up the text and other line work to be reproduced in an ordinary printing form. This form is then inked and an impression on paper is made therefrom. Finally, the inked imprint or impression is photographed to produce the transparency.

There are serious disadvantages to the above procedure of forming the line work transparency. Regardless of how well type, type-slugs, and printing plates are made, there is a substantial loss in the clarity of the outlines in the printing surfaces thereof during the inking and during the actual printing operation, and this loss is carried over in any photographic operation which involves photographing an inked impression from such type or other printing surfaces. Also, the process requires careful make-ready of the printing form, inking of the form, and the making of an impression on paper, all of which steps involve considerable time and require relatively skilled workmanship.

It is apparent that many of the difficulties inherent in the above described procedure of forming a transparency of the line work, and most of the disadvantages of that procedure could be avoided by the direct photographing of the printing form, and in the past, many attempts have 2,751,294 Patented June 19, 1956 been made to do this. However, due at least in part to the fact that a printing form is commonly made up of elements having very uneven reflecting powers, varying from the high reflectance of new, cast type or type-slugs, to the low reflectance characteristics of, for example, an oxidized copper plate, very poor results have generally been obtained in direct photography procedures. In fact, the results have generally been so unsatisfactory that for many years it was thought that the direct photography of printing forms was impractical and even impossible.

One successful procedure which makes it possible to directly photograph the relief printing surfaces contained in the usual printing form, which may include type of various kinds and varieties and printing plates made of various metals is disclosed in my prior application Serial No. 303,391, now Patent No. 2,704,410, of which the present application is a continuation-in-part. However, it was still considered necessary to form separate transparencies of some of the half-tone images and then combine these with the transparency formed from photographing the printing form in a stripping operation. Although various attempts have been made to photograph paper copy and/ or proofs of half-tone work, none have proven successful. In each case, there was a considerable loss of tonal values and increased contrast in the transparency for reasons which will hereinafter be made clear. This loss of tonal values and increased contrast was so serious that the photographing of paper copy and/or proofs of half-tone work was considered impractical.

It is generally the object of the present invention to provide a procedure for simultaneous or double photographing of any combination of relief printing surfaces with photographic half-tone reproductions and/ or photographic reproductions of line work so as to form a composite transparency suitable for use in the making of a press plate.

In accordance with the present invention, a transparency containing an image to be reproduced is com bined with a light reflective surface in a manner such that it may be photographed without the loss of tonal qualities or increase in contrast, together with relief printing surfaces, such as may be contained in the usual printing form, which are treated in the manner set forth in my said prior application, Serial No. 303,391, now Patent No. 2,704,410.

The present invention makes possible the obtaining of a much better composite transparency of both line and half-tone work than has been possible by any of the heretofore known procedures. The desired composite transparency can be made in a minimum amount of time and with a minimum amount of effort and equipment. Moreover, the practice of the invention does not impair the type or plates contained in the printing form and does not interfere with the prior or subsequent use of the form or its components.

Oother objects and features of the invention will be come apparent from the following description and accompanying drawings in which:

Figure l is a perspective view of a printing form containing various kinds of relief printing surfaces, together with a specially prepared photographic reproduction;

Figure 2 is a greatly magnified cross-sectional view of a half-tone image printed on a paper base indicating the manner in which the incident light rays which strike the paper base are reflected;

Figure 3 is a greatly magnified cross-sectional view of a film containing a half-tone image which has been coated with a reflective surface in accordance with the present invention;

Figure 4 is a greatly magnified cross-sectional view showing the coated film of Figure 3 with the addition of a base-board backing member which facilitates the bandling of the coated film; and

Figure is a greatly magnified cross-sectional view of a modified form of reflective reproduction formed in accordance with the present invention, said reflective reproduction being formed by mounting a strip film containing a half-tone image on a metal base.

The printing form illustrated in Figure l is of conventional type, and as such, it includes the usual heavy metal chase 11 for containing the various components of the form, furniture (i. e., spacers) 13 and the usual locking wedges or quoins 15 for holding the printing elements in place in the chase. The printing form may include newly cast type and/ or type-slugs, slightly used type, old type that is dirty and oxidized, photo-engravings, stereotypes,

:and other printing plates having surfaces which may be of copper, zinc, brass, steel, nickel, chrome, silver, etc. together with photographic images which are prepared in accordance with the present invention and mounted above a backing member formed of any suitable material such as metal, wood, etc. The type and/ or type-slugs and the stereotypes are all generally made of type metal. In the form illustrated in Figure 1, a copper printing plate is illustrated at 17, a zinc photo-engraving in which the background forms the relief printing surface at 19, an electrotype section at 21, a stereotype section at 2.3, a type seetion which may be either single type or type-slugs at 25,

and a specially prepared photographic reproduction at 27 Although the manner in which the various relief printing surfaces contained in the printing form are prepared for photographing is adequately described in my prior application, Serial No. 303,391, new Patent No. 2,7 04,410, it shall be repeated hereinafter for the sake of convenience. Initially, the printing form is set up with the backing members or blocks which support the photographic reproductions in position but without the photographic reproduction thereon. The various components or printing elements in the printing form are then treated in the following manner. First, the oxide coatings which are generally present on the relief printing surfaces of the printing elements are removed. The oxides are preferably rei moved from the surfaces of all the metals other than type metal in the printing form by chemical treatment. In order to minimize or prevent the reoxidation or spotting of the surfaces during this process, as little water as possible should be present in the chemical solution used in the removal of these oxides.

tions, well known to those skilled in the art, can be used Common chemical soluto remove the oxides from the relief printing surfaces in the printing form. Volatile solutions are generally preferred since they shorten the time required for this operation. Examples of suitable solutions which may be used 7 to remove the oxides from copper and zinc are: a 5 per cent solution of hydrochloric acid in anhydrous alcohol f works very well on copper and to a lesser extent on zinc;

a per cent solution of sulphuric acid in anhydrous alcohol also works well on copper but is not as efficient as the hydrochloric acid solution; and a 10 per cent solution of acetic acid in anhydrous alcohol produces very satisfactory results on zinc.

The appropriate chemical solution can be applied to a printing surface by placing a small amount of the chemical solution on a rubber block by spraying, dabbing, or the like, and then passing this block over the printing surfaces. If the proper chemical solution is used, this treatprinting surfaces other than the type metal, the surfaces of all of the metals in the printing form are subjected to an abrasion treatment. This step serves the following function: it removes the oxide from the surfaces of any type metal which might be present in the printing form; it removes any oxide which might be reforming on the surfaces other than type metal in the printing form; and it converts each of the relief printing surfaces in the printing form into a substantially uniform matte finish which is a diffusively reflecting surface, fine enough to permit a high percentage of incident light to obey the cosine law. The resultant relief printing surfaces have sufficiently similar light reflectance characteristics to provide, after the hereinafter process steps are carried out, a composite surface suitable for photographing.

The abrading can be accomplished in various ways, however, particularly satisfactory results are obtained when the abrading is accomplished by the use of a clean, resilient surface such as a block of rubber or rubber-like compound, containing fine abrasive particles therein. An ordinary pencil eraser is an example of such material, although a larger block such as is commonly used in the jewelry polishing industry will be found more practical in commercial operations. The abrasive material contained in the resilient block is preferably very fine, such as flour of emery, diatomaceous earth and the like. As previously stated, abrading removes dirt, oxides and the like and converts the relief printing surfaces in the printing form to clean matte surfaces having uniform light diffusion properties. For best results, the abrasive produced matte surfaces should not contain any lines large enough to be visible by the naked eye. A few light strokes of the abrasive carrying block across the raised printing surfaces in the printing form are usually sutficient to produce the desired result. As the abrasive carrying resilient block is used, metallic particles are transferred from the printing surfaces to its surface, thereby causing its surface to become contaminated or loaded? After a short time, the surface of the resilient block would, if not cleared, become sufliciently contaminated to act as a polishing surface rather than as an abrading surface. It is therefore necessary to frequently clean the surface of the resilient block so as to assure that it acts as an abrading surface. Both the cleaning and abrading operations can be accomplished in a very short interval of time.

After the abrading operation is completed,'thc entire printing form is coated with a light absorbing or non actinic coating, preferably .by spraying, although this coating can be applied in any other manner. Various materials can be used for the light absorbing coating; the best coatings, however, are those which include a suitable light absorbing pigment dispersed in a suitable liquid vehicle. The sprayed coating should dry rapidly and should be readily removable from the printing surfaces, as is required in the next step of the preparation process. The sprayed coating should also be readily removable so that the printing form and the printing elements therein can be cleaned at the conclusion of the photographing operation. At the same time, the coating should not dust or crack and should not be toxic or difficult to use.

A particularly satisfactory coating is produced by a mixture of two parts of trichlorethylene and one part lamp black, all parts being by volume. This mixture is cheap and easy to handle. The resultant coating dries immediately, is easily removed from the type and printing plate surfaces, and does not dust or crack.

Other typesof coatings may, of course, be used. The

' essential thingis the provision of a coating which will not the metallic. oxides reflect actinic light. For example, it is possible to employ an alcohol base coating, a suitable formula includes one part shellac, six parts dry drop-black, and eight parts methanol, all parts being by volume. This coating dries very fast, but in order to make the coating easily removable from the printing surfaces which are to be photographed, it is necessary to ink the printing form before the coating is applied. It is also possible to use coatings which comprise dispersions of pigments other than dropblack, for example, red lead can be used quite successfully. Also, it is possible to spray the printing form with an optical black lacquer, but materials of this type are not recommended because of the difficulties experienced in cleaning the type and other printing elements in the printing form.

As a final step in the preparation of the printing surfaces, the non-refiecting coating which has been applied to the entire surface of the printing form is removed from the relief printing surfaces of the printing form. The nonreflecting coating which remains thus masks or covers the entire background of the printing form while the metallic printing surfaces are completely exposed.

The removal of the non-reflecting coating from the printing surfaces is conveniently accomplished by the use of a flat rubber pad, a cloth-covered, rather firm, rubber block, or equivalent means. If the coating has been applied by the use of the trichlorethylene lamp black mixture described above, the pad may be used dry and a few light strokes thereof will effect adequate cleaning of the printing surfaces. On the other hand, if an alcohol type coating is used, the printing form should be inked preliminary to the application of the coating and the coating may be removed by using a soft pad which has been moistened in naptha, benzene, or other ink solvent.

Various changes may be made in the order of the various steps of preparing the printing surfaces in the printing form. For example, the abrading step or the chemical treatment step and the abrading step can be carried out after the non-actinic coating has been applied to the entire surface of the printing form and then removed from the printing surfaces. However, when the steps are reversed in this manner, there is some danger that the nonactinic coating will be rubbed elf of the background of the printing form.

After the printing elements in the printing form are treated in the above manner, photographic reproductions which are especially prepared in the manner set forth below may be positioned within the printing form on the surface of an underlying supporting block which also serves to properly space and position the printing elements in the printing form. Since the printing elements in the printing form are generally laterally reversed, the images in the photographic reproductions should likewise be laterally reversed. The supporting block is of appropriate height so as to position the reflective surface of the photograph reproduction at approximately the same height as the printing surfaces of the printing form. The manner of preparing a photographic reproduction so that it may be either simultaneously or double photographed (a double exposure taken on the same film) with the prepared printing surfaces in the printing form is described in detail below.

In order to understand the necessity of preparing a photographic print in the manner to be described, it will be helpful to understand why there is a considerable loss of tonal values with resulting increased contrast when a proof of a letter press half-tone image is photographed. The main cause of this loss of tonal values arises from the reflection characteristics of the proof or paper base print. This phenomena is illustrated in Figure 2 wherein a print of a half-tone image 31 is shown on a paper base 33 which is both li ht reflective and light permeable. When the image 31 on the paper base is illuminated with a diffused source of light, the light rays strike the surface of the print at various angles. The light rays which strike the print at an angle normal to the surface of the print are generally either absorbed or reflected, depending upon whether the rays strike the black dots 35'which form the image 31 or the area 37 between the dots 35. Where the light rays strike the surface of the print at an angle other than normal to the surface, the reflection characteristics are not ideal. In Figure 2, there is illustrated a pair of light rays A1 and A: striking the surface of the print at the same angle. The ray A1 strikes the surface of the print at a point spaced from the dots 35 and is partially reflected along a line B1. Some of the incident light, however, penetrates the paper base 33 where it is diffused and reflected along lines such as for example line C1. The ray of light A2 on the other hand, strikes the print near several of the half-tone dots 35. A portion of the light of the ray A2 is reflected from the surface of the print along a line B2 and a portion of the light is internally reflected along lines such as for example C2 within the paper base and absorbed by one or more of the black dots 35. Thus, where the dots 35 are close together as at D, there is less light being reflected back to the viewer than occurs in those areas as at E where the dots 35 are further apart. The result is a loss in tonal values or increase in contrast in the shadow and middle tonal values of the photographic image. The same is true, of course, when a transparent photographic image is mounted on a paper base and photographed.

The present invention overcomes the above difiiculties and provides an accurate means for photographing halftone, line, or other forms of photographic images. This is accomplished by first producing an image of the desired form on a transparent base and then applying a light reflective, light impervious surface to the transparent base which contains the image with the light reflective surface in intimate contact with the image. This provides an image which can be photographed without loss of tonal values.

Many methods are available for applying a light reflective surface to a transparent base for the purpose of this invention. One of the easiest methods involves spraying or brushing a liquid composition containing light reflective particles such as aluminum particles or similar bright metallic particles on the base and in contact with the image therein. Ordinary aluminum paint or lacquer, for example, has been found to be satisfactory for this purpose. It has been found necessary to apply the liquid composition in a very thin layer so as to prevent stratification between the metallic particles and the liquid vehicle.

When the transparent base containing the image consists of strip film, the light reflective surface may be pro vided by securing the strip film to a highly polished surface as, for example, a highly polished sheet of aluminum or tin foil, metal acetate sheeting, or other metallized surface.

For the purpose of the present invention, it is essential that the light reflective surface be in intimate contact with the image. Where the image is produced on an extremely thin film such as ordinary strip film, either side of the film may be secured to the light reflective surface. However, when the transparent base has an appreciable thickness, of the order of a few mils, it becomes important to apply light reflective surface to the surface which contains the image. In the case of an ordinary photographic film, this means that the light reflective surface must be applied to the emulsion surface of the film and that the image be subsequently photographed through the transparent base which overlies the image.

Three examples of transparent photographic images which are provided with light reflective surfaces in accordance with the present invention are illustrated in Figures 3, 4, and 5. In Figure 3, the reference numeral 39 indicates a film base having an emulsion surface 41 which includes a half-tone image 43.- A light reflective metal coating 45 covers the entire emulsion'surface 41. This light reflective coating may be formed of a material such as aluminum powder and be applied to the emulsion surface 41 by spraying, brushing, roller coating, etc.

It is generally preferable to mount a coated transparency such as is illustrated in Figure 3 on a supporting member 47 formed of press board, cardboard, metal, or the like as shown in Figure 4 so as to maintain the coated transparency in as flat a condition aspossible.

of extremely small thickness which includes a half-tone image 51 is adhesively secured to a metal supporting a member 53 which may consist of any light reflective metal such as a bright, metallic coated plate, a metal sheet, or a metal foil.

The coated films described above may be photographed in the usual manner without any noticeable loss of tonal values since practically all of the light rays such as the rays F and H, which strike the reflective surface between the dots of the half-tone images are reflected back along lines such as the lines G and I with the same intensity.

When the coated, transparent reproduction is combined with other printing elements for simultaneous photographing, it is, of course, necessary to have the reflection characteristics of the transparent reproduction match that of the other printing elements. It has been found that the re- .fiectance characteristics of both the transparent reproduction and the printing elements are approximately the same -when they are prepared in the manner described above.

However, even better matching of the reflection characteristics is obtained when the upwardly facing surface of the transparent reproduction (i. e., when the surface of the reproduction opposite that to which the light reflective -material is applied) is abraded. The abrading can be accomplished in various ways and particularly satisfactory results are obtained when the surface is abraded by the use of a cotton pad containing pumice particles or by the use of a block of rubber or rubber-like compound containing very finely divided abrasive material. The abrading transforms the upper surface of the film or transparency into a matte finish, that is, a uniform, ditfusively reflecting surface.

If the coated transparent reproduction is to be inserted in the printing form, the image therein should be laterally .reversed and the transparent reproduction should be of suitable dimensions for insertion in the desired location within the printing form. A convenient method of positioning the coated transparency within the printing form his to place suitably-sized strips of double faced Scotch j tape, that is, Scotch tape which has an adhesive surface on both of its sides, on the back side of the reflective surface or the supporting member which is secured to the reflective surface, drop a few drops of trichloroethylene onto the black coated base, and then place the coated transparent reproduction in the selected location within the printing form and press downwardly. There will be sufiicient adherence between the Scotch tape and the underlying block due to the trichloroethylene softening 1 both the black coating and the Scotch tape adhesive to prevent the dislocation of the mounted transparent reproduction during the subsequent photographing operation. The mounting block should be of suitable height so that the reflective surface to which the transparent reproduction is bonded lies at approximately the same height as-the relief printing surfaces within the printing form.

After the transparency is mounted within the printing form, the form is ready for photographing. This may be effected by the use of an ordinary photo-engravers camera or similar equipment. One particularly effective arrangement has been described in my prior patent, No. 2,609,623.

In certain cases, such as where illustrations fit close to type, where type is set irregularly around an illustration,

where it is desired to have type overprint illustrations,

' etc., the above described procedure cannot be followed.

in these special cases, it is necessary to prepare the printing form and the transparencies in the manner described. above but instead of placing the prepared transparency in the printing form for subsequent simultaneous photographing, the printing form and prepared transparencies are maintained as separate entities and photographed .iseparately. on the same film by double exposing the film;

The printing form and the reflective images must be properly positioned during the. photographing so that they register properly on the double exposed film. If desired,

printed with the printing form, must also be laterally reversed so they will read the same as the printing form (which is wrong-reading). These laterally reversed images can generally be made from conventional copy and standard cameras by means of a prism, a straightline image reverser, or by photographing on strip film and then flopping the film. There are other means of obtaining laterally reversed images, such as making a contact print on Autopositive film.

in the foregoing, there has been described an improved method of preparing printing elements and photographic reproductions for either simultaneous or double photographing. The practice of the invention provides a convenient and economical means for producing transparencies of both line and half-tone images for subsequent use in preparing press plates.

It will be appreciated that various modifications can be made to the above described method without departing from the scope of the present invention.

The present invention is a continuation-in-part of my prior application, Serial No. 303,391, filed August 8, 1952, now Patent No. 2,704,410, which in turn was a continuation-in-part of an earlier application, Serial No. 20,214, filed April 10, 1948, now Patent No. 2,624,700.

1 claim:

1. The method of obtaining a film transparency having a plurality of images arranged into a montage formed therein from printing elements which have relief printing surfaces and transparent bases which have images formed therein, comprising the steps of, assembling selected printing elements into a printing form with all of the relief printing surfaces of said printing elements at approximately the same height, abrading the relief printing surfaces with a clean, resilient surface containing very fine abrasive particles therein to produce on said relief printing surfaces a clean, diifusively reflecting finish of sufficient fineness so that the individual lines in the surfaces are not visible to the naked eye, applying a light absorbing coating to the entire surface of the printing form, removing said coating from the relief printing surfaces while leaving the coating intact on the other surfaces of the printing form, applying a light reflective surface onto at least one of said transparent bases in intimate contact with the image formed therein, and then photographing said prepared printing form and each rcflectively surfaced, transparent base on the same photographic film and in suitable registration.

2. The method of obtaining a film transparency having a plurality of images arranged into a montage formed therein from printing elements which have relief printing surfaces and transparent bases which have images formed therein, comprising the steps of, assembling selected printing elements into a printing form with all of the relief printing surfaces of said printing elements at approximately the same height, applying a light absorbing coating to the entire surface of the printing form, removing said coating from the relief printing surfaces while leaving the coating intact on the other surfaces of the printing form, abrading the relief printing surfaces with a clean, resilient surface containing very fine abrasive particles therein to produce on said relief printing surfaces a clean, ditfusively reflecting finish of sufficient fineness so that the individual lines in the surfaces are not visible to the naked eye, applying a light reflective surface onto at least one of said transparent bases in intimate contact with the image formed therein, and then photographing said prepared printing form and each reflectively surfaced, transparent base on the same photographic film and in suitable registration.

3. The method of obtaining a film transparency having a plurality of images arranged into a montage formed therein from printing elements which have relief printing surfaces and transparent bases which have images formed therein, comprising the steps of, assembling selected printing elements into a printing form with all of the relief printing surfaces of said printing elements at approximately the same height, abrading the relief printing surfaces with a clean, resilient surface containing very fine abrasive particles therein to produce on said relief printing surfaces a clean, diffusively reflecting finish of sufficient fineness so that the individual lines in the surfaces are not visible to the naked eye, applying a light absorbing coating to the entire surface of the printing form, and then removing said coating from the relief printing surfaces While leaving the coating intact on the other surfaces of the printing form, applying a thin film of light reflective metal particles onto at least one of said trans parent bases in intimate contact with the image formed therein, and then photographing said prepared printing form and each reflectively surfaced, transparent base on the same photographic film and in suitable registration.

4. The method of obtaining a film transparency having a plurality of images arranged into a montage formed therein from printing elements which have relief printing surfaces and transparent bases which have images formed therin, comprising the steps of, assembling selected printing elements into a printing form with all of the relief printing surfaces of said printing elements at approximately the same height, abrading the relief printing surfaces with a clean, resilient surface containing very fine abrasive particles therein to produce on said relief printing surfaces a clean, diifusively reflecting finish of sufiicient fineness so that the individual lines in the surfaces are not visible to the naked eye, applying a light absorbing coating to the entire surface of the printing form and then removing said coating from the relief printing surfaces while leaving the coating intact on the other surfaces of the printing form, applying a light reflective surface onto selected transparent bases in intimate contact with the images formed therein, abrading the surfaces of said selected transparent bases which are opposite to said light reflective surfaces, and then photographing said prepared printing form and each of said abraded and reflectively surfaced transparent base in the same photographic film and in suitable registration.

5. The method of obtaining a film transparency having a plurality of images arranged into a montage formed therein from printing elements which have relief printing surfaces and transparent bases which have images formed therein, comprising the steps of, assembling selected printing elements into a printing form with all of the relief printing surfaces of said printing elements at approximately the same height, abrading the relief printing surfaces with a clean, resilient surface containing very fine abrasive particles therein to produce on said relief printing surfaces a clean, diffusively reflecting finish of sufificient fineness so that the individual lines in the surfaces are not visible to the naked eye, applying a light absorbing coating to the entire surface of the printing form, removing said coating from the relief printing surfaces while leaving the coating intact on the other surfaces of the printing form, applying a thin film of light reflective metal particles onto selected transparent bases in intimate contact with the images formed therein, abrading the surfaces of said selected transparent bases which are opposite to said light reflective surfaces and then photographing said prepared printing form and each of said abraded and reflectively surfaced transparent base in the same photographic film and in suitable registration.

6. The method of obtaining a film transparency having a plurality of images arranged into a montage formed therein from printing elements which have relief printing surfaces and transparent bases which have images formed therein, comprising the steps of, assembling selected printing elements into a printing form with all of the relief printing surfaces of said printing elements at approximately the same height, removing the oxides from each of the relief printing surfaces of the printing form, abrading the relief printing surfaces with a clean, resilient surface containing very fine abrasive particles therein to produce on said relief printing surfaces a clean, diffusively reflecting finish of suificient fineness so that the individual lines in the surfaces are not visible to the naked eye, applying a light absorbing coating to the entire surface of the printing form, removing said coating from the relief printing surfaces while leaving the coating intact on the other surfaces of the printing form, applying a light reflective surface onto at least one of said transparent bases in intimate contact with the image formed therein, and then photographing said prepared printing form and each reflectively surfaced, transparent base on the same photographic film and in suitable registration.

7. The method of obtaining a film transparency having a plurality of images arranged into a montage formed therein from printing elements which have relief printing surfaces and transparent bases which have images formed therein, which comprises the steps of, assembling various desired relief printing surfaces into a printing form with all of the relief printing surfaces at approximately the same height, abrading the relief printing surfaces with a clean, resilient surface containing very fine abrasive particles therein to produce on said relief printing surfaces a clean, difiusively reflecting finish of sufficient fineness so that the individual lines in the surfaces are not visible to the naked eye, applying a light absorbing coating to the entire surface of the printing form, re moving said coating from the relief printing surfaces while leaving the coating intact on the other surfaces of the printing form, applying a light reflective surface onto desired transparent bases in intimate contact with the images formed therein, mounting said reflectively surfaced transparent bases in selected positions within said printing form with said light reflective surfaces lowermost and at approximately the height of said relief printing surfaces, and then photographing said printing form.

8. The method of obtaining a film transparency having a plurality of images arranged into a montage formed therein from printing elements which have relief printing surfaces and transparent bases which have images formed therein, which comprises the steps of, assembling various desired relief printing surfaces into a printing form with all of the relief printing surfaces at approximately the same height, applying a light absorbing coat ing to the entire surface of the printing form, removing said coating from the relief printing surfaces while leaving the coating intact on the other surfaces of the printing form, abrading the relief printing surfaces with a clean, resilient surface containing very fine abrasive particles therein to produce on said relief printing surfaces a clean, diffusively reflecting finish of sufficient fineness so that the individual lines in the surfaces are not visible to the naked eye, applying a light reflective surface onto desired transparent bases in intimate contact with the images formed therein, mounting said reflectively surfaced transparent bases in selected positions within said printing form with said light reflective surfaces lowermost and at approximately the height of said relief printing surfaces, and then photographing said printing form.

9. The method of obtaining a film transparency having a plurality of images arranged into a montage formed therein from printing elements which have relief printing surfaces and transparent bases which have images formed therein, which comprises the steps of, assembling various desired relief printing surfaces into a printing form with all of the relief printing surfaces at approxiare not visible to the naked eye, applying a light absorbing coating to the entire surface of the printing form, removing said coating from the relief printing surfaces while leaving the coating intact on the other surfaces of the printing form, applying a thin film of light reflective metal particles onto desired transparent bases in intimate contact with the images formed therein, mounting said refiectively surfaced transparent bases in selected positions within said printing form with said light reflective surfaces lowermost and at approximately the height of said relief printing surfaces, and then photographing said printing form.

10. The method of obtaining a film transparency having a plurality of images arranged into a montage formed therein from printing elements which have relief printing surfaces and transparent bases which have images formed therein, which comprises the steps of, assembling various desired relief printing surfaces into a printing form with all of the relief printing surfaces at approxirnately the same height, abrading the relief printing surfaces with a clean, resilient surface containing very fine abrasive particles therein to produce on said relief printing surfaces a clean, diffusively reflecting finish of sufficient fineness so that the individual lines in the surfaces are not visible to the naked eye, applying a light absorbing coating to the entire surface of the printing form, re-

moving said coating from the relief printing surfaces while leaving the coating intact on the other surfaces of the printing form, applying a light reflective surface onto desired transparent bases in intimate contact with the images formed therein, abrading said desired transparent Y bases on the surfaces opposite to said light reflective surfaces, mounting said abraded and refiectively surfaced transparent bases in selected positions within said printing form with said light reflective surfaces lowermost and at approximately the height of said relief printing surfaces, and then photographing said printing form.

11. The method of obtaining a film transparency having a plurality of images arranged into a montage formed therein from printing elements which have relief printing surfaces and transparent bases which have images formed therein, which comprises the steps of, assembling various desired relief printing surfaces into a printing form moving said coating from the relief printing surfaces while leaving the coating intact on the other surfaces of the printing form, applying a thin film of light reflective metal particles onto desired transparent bases in intimate contact with the images formed therein, abrading the surfaces of said desired transparent bases which are opposite to said light reflective surfaces, mounting said abraded and reflectively surfaced transparent bases in selected positions within said printing form with said light reflective surfaces lowermost and at approximately the height of said relief printing surfaces, and then photographing said printing form.

12. The method of obtaining a film transparency having a plurality of images arranged into a montage formed therein from printing elements which have relief printing surfaces and transparent bases which have images formed therein, which comprises the steps of, assembling various desired relief printing surfaces into a printing form with all of the relief printing surfaces at approximately the same height, removing the oxides from each of the relief printing surfaces of the printing form, abrading the relief printing surfaces with a clean, resilient surface containing very fine abrasive particles therein to produce on said relief printing surfaces a clean, difiusively reflecting finish of sufiicient fineness so that the individual lines in the surfaces are not visible to the naked eye, applying a light absorbing coating to the entire surface of the printing form, removing said coating from the relief printing surfaces while leaving the coating intact on the other surfaces of the printing form, applying a light reflective surface onto desired transparent bases in intimate contact with the images formed therein, mounting said reflectively surfaced transparent bases in selected positions within said printing form with said light reflective surfaces lowermost and at approximately the height of said relief printing surfaces, and then photographing said printing form.

References Cited in the file of this patent UNITED STATES PATENTS 1,669,821 Grass May 15, 1928

Claims

1. THE METHOD OF OBTAINING A FFILM TRANSPARENCY HARVING A PLURALITY OF IMABES ARRANGED INTO A MONTAGE FORMED THEREIN FROM PRINTING ELEMENTS WHICH HAVE RELIEF PRINTING SURFACES AND TRANSPARENT BASES WHICH HAVE IMAGES FORMED THEREIN, COMPRISING THE STEPS OF, ASSEMBLING SELECTED PRINTING ELEMENTS INTO A PRINTING FORM WITH ALL OF THE RELIEF PRINTING SURFACE OF SAID PRINTING ELEMENTS AT APPROXIMATELY THE SAME HEIGHT, ABRADING THE RELIEF PRINTING SURFACES WITH A CLEAN, RESILIENT SURFACE CONTAINING VERY FINE ABRASIVE PARTICLES THEREIN TO PRODUCE ON SAID RELIEF PRINTING SURFACES A CLEAN, DIFFUSIVELY REFLECTING FINISH OF SUFFICIENT FINENESS SO THAT THE INDIVIDUAL LINES IN THE SURFACES ARE NOT VISIBLE TO THE NAKED EYE, APPLYING A LIGHT ABSORBING COATING TO THE ENTIRE SURFACE OF THE PRINTING FORM, REMOVING SAID COATING FROM THE RELIEF PRINTING SURFACES WHILE LEAVING THE COATING INTACT ON THE OTHER SURFACES OF THE PRINTING FORM, APPLYING A LIGHT REFLECTIVE SURFACE ONTO AT LEAST ONE OF SAID TRANSPARENT BASES IN INTIMATE CONTACT WITH THE IMAGE FORMED THEREIN, AND THEN PHOTOGRAPHING SAID PREPARED PRINTING FORM AND EACH REFLECTIVELY SURFACE TRANSPARENT BASE ON THE SAME PHOTOGRAPHIC FILM AND IN SUITABLE REGISTRATION.