GB2068572A - Combined contact and projection printing - Google Patents

Abstract

Photographic material 6 is exposed simultaneously to a contact image from a transparency 12 bearing half-tone material and to a projected image from a paste-up sheet 5 bearing artwork and/or text 9/10 and a blank strongly reflective area 5 corresponding to the half-tone material. Sheet 5 is registered by placing on pins 7. The transparency is registered by first placing on pins 7 in order to register the half-tone material with blank area 5 (the transparency comprising half-tone material adjustably attached by adhesive tape to a clear carrier sheet), whereafter the transparency is transferred to pins 8. <IMAGE>

Description

SPECIFICATION Camera and method of operating it This invention relates to camera and methods of operating them.

In order to prepare photographically an image whether positive or negative for a page of material containing both art work or printing and a halftone picture printers usually prepare a positive of the half-tone picture and prepare separately the art work which is to go on the page and stick them all onto backing sheet. This paste-up is then photographed to produce a photographic record which can then by used in platemaking, photographic or other reproduction process.

Many printers cannot afford high precision camers for the operation of photographing the paste-up and resort to the use of comparatively low priced fixed-focus cameras and also to the use of comparatively low priced film, especially a type of film called "stabilisation" film which carries within it its own processing materials so that moistening or washing preferably in a special bath constitutes all the development process that is necessary, at least where only short term storage is desired.

These expedients although unavoidable for most printers from the economic point of view do mean that there will be a loss of quality in the reproduction of the half-tone image and indeed it is well known that with some types of film, screen rulings finer than 100 lines per inch (40 lines/cm) cannot bye used; while of course screens of larger dot sizes give a comparatively coarse appearance to the finished work.

The present invention shows how while continuing to use a camera, usually a fixed-focus camera, and comparatively low resolution film, one can achieve a higher degree of accuracy in the half-tone work and therefore enable the use of finer half-tone screens in the preparation of that work.

I achieve this by photographing the material of the paste-up simultaneously by two different ways. Art work and other non-half-tone material on the paste-up is photographed in the conventional way through the lens of a camera.

The half-tone material is however photographed by contact printing onto the same photographic material as is simultaneously receiving the image of the paste-up through the lens. If the paste-up sheet is left blank in the position corresponding to that in which an image of the half-tone matter is required it will give by reflection from the light sources which are illuminating the paste-up sheet enough exposure light for carrying out the contact printing.

In a camera designed to achieve this, I provide registration means on the work table which is to carry the paste-up sheet and at the level of the film carrier which supports the photographic material. These registration means are to allow a carrier sheet carring half-tone material to be transferred in exact register from a place where it is prepared when superposed over the paste-up sheet to below the film and thereby to assure that the contact printing on the film occurs in a position corresponding exactly to that desired on the paste-up sheet. Because the camera is fixedfocus (or of variable focus but with means such as a catch for precisely defining a given position), the desired relative position can be achieved by this simple means.

A particular embodiment of the invention will now be described with reference to the accompanying drawings wherein: Figure 1 is a perspective and highly diagrammatic view of a fixed4ocus camera embodying the invention, and Figure 2 is a section in the plane Il-Il Fig. 1 to show also diagrammatically the operation of the invention.

In Fig. 1 a fixed-focus camera has a copy holder 1, an objective lens 2 and a film holder frame 3.

Through the window 4 of the film holder, light transmitted from an image 5 on the work table is focussed by the lens 2 onto the focal plane of the camera at which there is placed photographic material which is a film or plate 6.

In the invention, registration means here shown as pins or pegs 7 and 8 are provided on the work table 1 and one the film holder 3 respectively.

Fig. 1 shows a paste-up 5 having art work or text 9, 10 and being held in a fixed position relative to the lens 2 by an integral or attached carrier portion -1 1 impaled on the register pin 7. In the head of the camera, there is interposed between the film 6 and the film holder 3 a clear transparent sheet 12 bearing on it a half-tone positive 13 (shown in dot-dash lines) which is sandwhiched between the clear sheet 12 and the film 6.

This situation is seen more clearly in Fig. 2 where of course the thickness of those layers are greatly exaggerated for clarity.

The film may alternatively be held by the application of reduced pressure to a flexible sheet to hold it to the holder, in this case known as a platen.

Exposure times and conditions are set up exactly as usual. The image of art work 9 and 10 is projected onto the film 6 by the fixed-focus lens 2 in the normal manner. However, the area 1 5 which is to be occupied by the half-tone image 1 3 is left blank on the paste-up sheet 5 and there is strong reflection from that area through the lens 2 towards the positive half-tone transparency 13.

This is, for a properly prepared positive, sufficient to cause a correct contact printing of that transparency onto the film 6 at the same time as the lens-transmitted image of the art work is being formed.

A high degree of resolution of the half-tone material is therefore obtained since its imagebearing layer is in direct contact with the photographic iayer of the film or plate 6.

The provision of registering means such as pins 7, 8 coupled with careful preparation of the position of the half-tone material 1 3 on the carrier sheet 1 2 ensures proper registration in the finished negative image formed on the film or plate.

Preparation of the record is as follows: The non-half-tone art work is prepared on the paste-up sheet 5 leaving those areas such as 1 5 blank which are to receive half-tone work in the finished page. Either directly or via a carrier sheet the paste-up is then placed in register with the registration means 7 provided on the work table, and the clear carrier sheet 12 is also placed on that registration means 7 and over the paste-up.

Then, the half-tone material 1 3 is fixed by adhesive tape or the like to the clear carrier sheet 12 in the position which is desired on the final image. The clear carrier sheet with the half-tone work is then transferred to the head of the camera and by the registration means 8 there provided (which correspond in nature and position to those on the table) is positioned relative to the image which is to be formed by the camera. The photographic material 6 is then placed in contact with the half-tone material 13 and clear screen in the focal plane of the camera and the exposure is made.

Claims (7)

1. A method of preparing a photographic record of material containing both i) half-tone and ii) artwork and/or printing, which includes exposing photographic material through a camera lens to light emanating from the artwork and/or printing copy to form a focussed image on the photographic material and simultaneously contact-printing half-tone transparency onto the same photographic material.

2. A method according to claim 1 wherein the artwork and/or printing is on a paste-up including a blank area corresponding to that to be occupied by the half-tone, whereby light emanating from that blank area and passing through the camera lens penetrates the half-tone transparency to effect the said contact-printing.

3. A method according to claim 1 or claim 2 wherein the camera is a fixed-focus camera.

4. A method according to claim 1, claim 2 or claim 3 wherein the photographic material is a stabilisation film.

5. A method substantially as herein described with reference to the accompanying drawings.

6. A camera adapted for carrying out the method according to any one of the proceding claims and including registration means both at a holder for the photographic material and at a table for the copy, whereby a half-tone transparency may be caused to adopt a position in contact with the photographic material corresponding to a predetermined position on the copy.

7. A camera substantially as herein described with reference to and as illustrated in the accompanying drawings.