GB2075215A - Photographic reproduction - Google Patents

Abstract

A process for producing a photographic reproduction of an original comprises combining a photographic screened reproduction with light and dark line reproductions. The resulting photographic reproduction has good clarity and definition and is suitable for the production of printing blocks. The screened reproduction is a positive and the line reproductions are formed by superimposing unexposed film with respective positive and negative derivations of the screened reproduction. The resulting photographic reproduction is formed by exposing unexposed duplicating film firstly in register with the screened reproduction and the dark line reproduction and secondly in register with the line reproductions, and then developing the duplicating film. Alternative methods of forming the line reproductions are disclosed.

Description

SPECIFICATION Photographic reproduction This invention relates to a photographic reproduction process, particularly for use in the formation of printing plates or blocks.

A printing plate or block may be formed from a photograhic reproduction which is obtained by a photographic process using a screen such that tone variations are represented by variations in intensities of dot or line shadings or the like. With this process however the problem arises that definition and clarity are poor having regard to the disruption of lines by the shading elements.

An object of the present invention is to overcome or at least appreciably reduce this problem.

According to the invention therefore there is provided a process for producing a photographic reproduction of an original comprising the steps of: producing a photographic screened reproduction of the original, producing respective light and dark photographic line reproductions of the original, and producing from a combination of the said screened reproduction and the said line reproductions a resulting photographic reproduction having a screened image of the original with light and dark image lines superimposed thereon.

With this arrangement, it will be appreciated that it is possible to obtain a photographic reproduction which is suitable for use in the formation of a printing plate or block and which has good clarity and definition.

The said main photographic reproduction may be a positive and the said line reproductions may be made from this by appropriately superimposing and illuminating unexposed film with positive and negative derivations of the said screened reproduction.

The invention will now be described further in the following examples.

A screen positive A is made, using duplicating film, of an original which may comprise artwork against a suitable background. The original contains black and white and also intermediate grey tones and tone variations are reproduced on the monotone positive A in conventional manner by variations in dot or line shadings or the like.

Atoned lithographic film negative B is also made from the original, white areas being highlighted and black areas intensified. This negative B is developed so that middle range grey tones are retained whilst any lithographic film grain is eliminated.

A toned lighographicfilm C is made by vacuuming unexposed lithographic film on top of the negative B, replacing same in position in the camera with the original artwork still in its original position, and then subjecting the film to three different light exposures, namely: a main exposure, a short flash exposure with the original artwork masked out and a final exposure with the negative B removed. The film is developed so that middle range grey tones are retained whilst any lithographic film grain is eliminated. The resulting film C has high contrast. Film C is a combination of certain areas of the original artwork being retained in negative form, but with the majority of detail converted to positive form from negative B. It also retains, from the original, more of the detail lost on negative B.

A duplicating film contact D is made from film C with the exposed emulsion on film C facing away from the unexposed emulsion of the duplicating film.

A lithographic film E is also made from film C, again with the emulsion of film C facing away from the emulsion of the film. The film is over-exposed to give heightened detail on the resulting film E.

Middle range grey tone areas on film C are transferred to and amplified on films D and E whereby when these films are superimposed as described hereinafter, the overlapping grey regions can act to mask out unwanted areas and also to accentuate details in tone which would otherwise be lost or faint.

A black line negative F is made from the film D and film E by superimposing these in register with a clear acetate film sandwiched between them. This sandwich is arranged in contact with unexposed lithographic film with the film E facing unexposed film in a rotating vacuum frame with the film D facing upwardly towards a source of light set at a predetermined angle. The film is exposed and the resulting negative F has an image made up of black lines (on a clear background) which represent the outline and also detail of the original artwork.

A white line positive G is made from the film D and film E by sandwiching such films with an unexposed duplicating film in contact with the film D. The sandwich is placed in a rotating vacuum frame with film E facing upwards towards a source of light set at a predetermined angle. The film is exposed and the resulting positive G has an image made up of white lines (on a black background) which represent the outline and also details of the original artwork.

The acetate spacer described above in relation to the production of film F determines the strength of the line detail and also the strength of the lines on both the black line and white line films F, G can be varied as required by adjustment of the angle of light from the light source.

A final positive H is made from the screen positive A and the line films F,G. First, the screen positive A is sandwiched between a sheet of unexposed duplicating film and the line film F, and the sandwich is placed in a vacuum frame with the film F facing a source of light and is exposed. Second, the screen positive A is removed from the sandwich and replaced with the film G. The sandwich is then subjected to a second exposure in the vacuum frame, and the exposed duplicating film is removed and developed. The resulting positive H has an image made up of areas of screen shading in combination with black and white lines which give rise to excellent clarity and definition.

In a second example of a method in accordance with the invention a screen positive A is made, on duplicating film, of the tone original art work as in the previous example. Preferably the screen positive A retains image detail even in the highlighted areas.

Afairly light duplicating film D is taken off the original tone artwork plus two other duplicating films D having differing degrees of density and in consequence differing areas of detail. The required areas of detail of these further films D are stripped in on the first film D to produce one master film D. The toned lithographic film negative E is then taken away from master film D, adding extra image detail and minimising the amount of "Spotting-out" on unwanted or film grain areas.

Alternatively a toned lithographic film negative E may be made from the original.

Also, with the original tone artwork still in position in the camera from the preparation of screen positive A, a duplicate film D is made from the original. It is noted that negative E and film D do not contain any areas of tone, the tones of the original artwork being represented by solid areas with the softer tones of the original resulting in grainy areas in negative E and film D.

When films E and D are superimposed, as described below, the overlapping of the converted image areas on these films act to mask out unwanted areas which are transferred to films D and E as undesirable grainy areas.

To produce the black line negative F, film D and negative E, produced by either of the above alternatives are placed in register, with a clear acetate film spacer between, and with the exposed negative E emulsion in contact with unexposed lithographic film F emulsion. The assembly is then placed in a rotating vaccum frame with film D facing upwardly towards a light source, which is set at a predetermined angle, and then exposed.

To produce the white line positive G, film D and negative E are placed together, in register, with unexposed duplicating film G emulsion in contact with exposed film D emulsion. The assembly is placed in a rotating vacuum frame with negative E facing upwardly towards a light source, again set at a predetermined angle, and then exposed. The preferred angular setting is 45% but may be varied to influence the strength of line produced. Also the abovementioned acetate spacer is used to determine the strength of line produced.

A duplicate, or film, is taken off film D and preselected solid areas from this duplicate are stripped in onto black line negative F to give greater contrast on the final product and to preclude intensified solid areas from appearing as screened areas.

The image on film D is hand masked except for any preselected areas where it is preferred to expose and "burn out" the image on the highlighted areas of the original. This achieves clear white highlighted areas on the final product to give added contrast thereto.

Film D thus becomes "burn-out" film D'.

The final positive H is then formed as follows.

Firstly screen positive A is placed between unexposed duplicating film H and black line negative F in a vacuum frame, and then exposed. Secondly screen positive A is replaced by white line positive G and a second exposure made. Thirdly white line positive G is replaced by "burn-out" film D1 and a third exposure made. In each of these exposures negative F faces the light source. After these exposures, film H is removed and developed to form the final positive high definition product combining white and black line detail.

A printing block or plate can be made from the positive H in conventional manner.

Accurate alignment of films during performance of the above described process steps may be achieved using a standard punch register system.

The invention is not of course intended to be restricted to the details of the above embodiments which are described by way of example only. Thus for example, one of the three abovementioned exposures utilised in the production of film C may be omitted as desired and depending on the original toned artwork.

Claims (21)

1. A process for producing a photographic reproduction of an original comprising the steps of producing a photographic screened reproduction of the original, producing respective light and dark photographic line reproductions of the original and producing, from a combination of said screened reproduction and said line reproductions, a resulting photographic reproduction having a screened image of the original with light and dark image lines superimposed thereon.

2. A process according to claim 1 wherein said screened reproduction is a positive.

3. A process according to claim 2 wherein said line reproductions are produced from said screened reproduction.

4. A process according to claim 3 wherein said line reproductions are produced by superimposing and exposing unexposed film with respectively a positive derivation and a negative derivation of said screened reproduction.

5. A process according to any one of claims 1 to 4 wherein said resulting photographic reproduction is formed by exposing unexposed duplicating film firstly whilst placed in register with said screened reproduction and said dark line reproduction, and secondly whilst placed in register with said line reproductions, and then developing said duplicating film.

6. A process according to any one of claims 1 to 5 including the step of producing a toned lithographic film negative of said original.

7. A process according to claim 6 wherein said film negative is produced from said original and a toned lithographic film positive is produced from said film negative and said original.

8. A process according to claim 7 wherein said toned lithographic film positive is produced by successive exposures of unexposed lithographic film, firstly with said film negative and said original, secondly a repeat exposure with said original masked, and thirdly with said film negative removed.

9. A process according to claim 8 wherein a duplicating film contact is made from said film positive with the exposed emulsion of said film positive remote from the unexposed emulsion of said contact duplicating film.

10. A process according to claim 9 wherein a further lithographic film is made from said film positive with the exposed emulsion of said film positive remote from the unexposed emulsion of said further lithographic film.

11. A process according to claim 10 wherein said dark line reproduction is a negative made by superimposing in register said duplicating film contact, a clear acetate film, said further lithographic film, and unexposed lithographic film, and exposing said unexposed lithographic film.

12. A process according to claim 11 wherein said light line reproduction is a positive made by superimposing in register said further lithographic film, said duplicating film contact, and unexposed duplicating film, and exposing said unexposed duplicating film.

i3. A process according to claim 6 wherein said film negative is produced from said original and a duplicate film is made from said original.

14. A process according to claim 6 wherein a duplicate film is made from said original and said film negative is made from said duplicate film.

15. A process according to claim 14wherein said duplicate film is made by combining at least two duplicate films of differing degrees in density made from said original.

16. A process according to claim 13 or claim 15 wherein said dark line reproduction is a negative made by superimposing in register said duplicate film, a clear acetate film, said film negative and unexposed lithographic film, the exposed emulsion of said film negative being in contact with the unexposed emulsion of said unexposed lithographic film, and exposing said unexposed lithographic film.

17. A process according to claim 16 wherein said light line reproduction is a positive made by superimposing in register said duplicate film, said film negative and unexposed duplicating film, the unexposed emulsion of said unexposed duplicating film being in contact with the exposed emulsion of said duplicate film, and exposing said unexposed duplicating film.

18. A process according to claim 17 when dependent on claim 5 including exposing said duplicating film when exposed for said first and second times for a third time whilst placed in register with said dark line reproduction and a burn-out form of said duplicate film.

19. A process according to claim 18 wherein said burn-out form is made by masking said duplicate film in preselected areas and exposing the same whilst so masked.

20. A process for producing a photographic reproduction of an original substantially as hereinbefdre described with reference to any one of the examples given herein.

21. A photographic reproduction of an original produced in accordance with any one of the preceding claims.