WO1991002286A1

WO1991002286A1 - Photographic reproduction

Info

Publication number: WO1991002286A1
Application number: PCT/GB1990/001205
Authority: WO
Inventors: Glynne Roberts Lancaster
Original assignee: Mmco Limited
Priority date: 1989-08-02
Filing date: 1990-08-02
Publication date: 1991-02-21
Also published as: GB8917654D0

Abstract

In a method of producing a photographic reproduction from an original (30), such as a negative, transparency or internegative, the image on the original is digitised and stored electronically. The digitised image is displayed on a monitor (24), and modified by the operator using a computer (20) until the displayed image exhibits desired characteristics. Subsequently, an exposure is made from the original, using as the light source a display device (11) displaying an image which is controlled in dependence on information contained in the modified digitised image so that the print (40) eventually obtained corresponds to the modified image appearing on the monitor. The exposure is carried out in sequence through three colour filters (16). Apparatus for carrying out the method is disclosed.

Description

PHOTOGRAPHIC REPRODUCTION

This invention relates to a method of .and apparatus for photographic reproduction.

The invention relates in particular to a method of and apparatus for producing a photographic reproduction from an original. The original may take any suitable form, and may for example be a photographic negative, transparency or internegative, or art work. The reproduction may be a photographic print, display transparency, colour separation set, or any other suitable image-bearing carrier.

In preparing a photographic reproduction from an origin»al, various parameters of the final image can be controlled. In particular, the size, crop (i.e. the area of the image on the negative to be reproduced), density and contrast of the fin»al image .and, for a colour image, the colour balance and colour saturation, can be controlled. In addition, various special effects may be introduced during the reproduction process. In producing high quality photographic prints, particularly for professional photographers, this control of the process has been carried out by skilled technicians, working to instructions from the photographer as to the effect desired in the finished print. Even using the complex equipment which is available, this is a labour intensive and time consuming task requiring skilled staff and typically involving the technician in producing a number of proofs before the client is satisfied with the final print. The process may require the technician to-produce a mask to control the exposure of selected portions of the image (as in the so called "silver masking" technique) .

It is an object of this invention to provide a method of photographic reproduction which reduces the need for skilled technicians to operate the process.

This invention consists in a method of producing a photographic reproduction from an original bearing an image to be reproduced, comprising the steps of generating and storing a digitised image representative of the image on the original, displaying the digitised image, modifying the digitised image thereby to modify the displayed image until it exhibits desired characteristics, and exposing a light sensitive carrier to light from a light source transmitted through or reflected from the origin.al, the exposing step being carried out as a sequence of exposures in light of different colours, each exposure being controlled in dependence on information contained in the modified digitised image so that the reproduction obtained following the exposing step has characteristics corresponding to those of the displayed modified image.

The digitised image may be displayed, under the control of a computer, on, for ex»ample, a conventional visual display unit or monitor, and may be modified by the operator using a suitable input device, such as a keyboard or "mouse" connected to the computer, the computer being programmed to allow various parameters of the displayed image to be modified, so that the operator can adjust the parameters until the modified image displayed on the visual display unit exhibits the desired characteristics. In accordance with the invention, the light source comprises a display device arranged to display an image which, during the exposure is projected onto the original. The display devicemay, for example, be a cathode ray tube. The image displayed on the cathode ray tube can be controlled to control parameters of the exposure of the light sensitive carrier. For example, the brightness of different parts of the displayed image can be controlled.

The cathode ray tube or other device is controlled by a computer which receives information from the digitised image so that the print obtained from the exposed light sensitive carrier has the desired characteristics of the modified image displayed on the visual display unit.

Other parameters may similarly be controlled during the exposure. For example, the exJJbsure may be carried out using apparatus using lenses for projecting the image of the cathode ray tube or other display device onto the original, and for projecting the image on the original onto the light sensitive carrier, and a power driven mechanism for δdjusting the relative positions of the v»arious components undesr computer control, to control the size and crop of the image. The apparatus may also include a mechanism for introducing appropriate colour filters sequentially into the optical path, under control of the computer.

The image on the original may be digitised using any suitable apparatus, for example a conventional scanner. The original may be scanned sequentially through filters corresponding or complementary to those through which the exposures are to be made.

The invention enables a high quality photographic reproduction to be produced without involving a person skilled in conventional techniques. For example, in producing a photographic print from an original supplied by a photographer, the photographer could manipulate the image displayed on the visual display unit to provide the desired characteristics. The subsequent printing can then be carried out automatically under computer control.

Since the photographic reproduction is produced by exposing the light sensitive carrier to light transmitted through or reflected from the original, the resolution of the final reproduction is at least as high as that obtained using conventional techniques, and is not dependent on the resolution of the digitised image. The digitised image can be produced at a relatively low resolution, and it may in some circumstances be desirable to degrade the resolution of the image shown on the cathode ray tube or other display device in the exposing process, to simulate the effect of an unsharp silver mask.

The invention also includes apparatus for producing a photographic reproduction from a photographic original bearing an image to be reproduced, comprising means for generating and storing a digitised image representative of the image on the original, display means for displaying the digitised image, processing means modifying the digitised image in response to a manual input, to enable an operator to modify the displayed image until it exhibits desired characteristics, means for sequentially exposing a light sensitive carrier to light of different colours from a light source transmitted through or reflected from the original, and means for controlling the exposure in dependence on information contained in the modified - . -

digitised image so that the reproduction obtained following the exposure has characteristics corresponding to those of the displayed modified image.

The invention will now be described, by way of example, with reference to the accompanying drawings in which:

Figure 1 shows diagramatically the arrangement of components in an exposing unit of a photographic printing apparatus in accordance with the invention, and

Figure 2 is a block diagram of a monitoring unit of the apparatus. ^• -..

Referring to Figure 1, the exposing unit comprises a cathode ray tube 11, controlled by a computer 10, a lens 12 by means of which the image on the screen of the cathode ray tube can be projected onto a negative 30 held in a holder 13, a projection lens 14 which projects the image of the negative 30 onto sensitive photographic paper 40 in a holder 15, and a filter mechanism 16 for interposing filters between the cathode ray tube 11 and the negative 30. The filter mechanism 16 may, for example, consist of three filters, typically red, green and blue, through which the sensitive paper 40 can be sequentially exposed.

The lenses, the holders for the negative and sensitive paper and the filter mechanism may be the same as those of a conventional photographic-enlarger, with a cathode ray tube 11 taking the place of the usual light source. The components may be supported in the same way as in the conventional enlarger, with the relative positions of the components movable, for example to enable the image of the negative to be focused onto the sensitive paper. Suitable drive mechanisms, for example servo controlled electric motors, .sire provided to enable the relative positions of the various components to be adjusted under control of the computer 10. Unlike the light source in a conventional enlarger, the cathode ray tube is preferably movable.

Referring to Figure 2, the analysing and monitoring unit comprises a scanning device 21 and digitiser 22, for digitising the image on the negative 30, a frame store 23 for storing the digitised image, a monitor 24 for displaying the digitised image, a computer 20 (which may be the same as the computer 10 used in the exposing unit) , and an input device 25, such as a keyboard or "mouse", for supplying manual input to the computer.

The scanning device 21 can take any suitable form. For example, the device could include a photo cell or array of photo cells arranged to be exposed sequentially to light transmitted through different areas of the negative, three scans being made, through respective filters corresponding to those through which the exposure is to be made. Alternatively a television camera could be used to scan the negative and supply a signal to the digitiser 22. The signal from the digitiser 22 is processed by the computer 20, taking into account all the variables in the exposing unit as well as the characteristics of the light sensitive paper and variables in subsequent processing of the exposed paper, so as to display on the monitor 24 an image which corresponds to that which would be obtained by exposing the sensitive paper 40 to the negative 30, without any modification. The processing therefore needs to take into account the variables of the exposing unit. The digitised image as produced is stored in frame store 23 or in the computer itself, or in any other suitable storage medium.

The operator uses the input device 25 to manipulate the image displayed on the monitor 24, under control of the computer software, to vary one or more of the parameters of the image, such as size, crop, density, contrast, colour balance and colour saturation, until the image has the desired characteristics. The modified image is stored in the frame store 23.

In subsequent use of the exposing unit, the original is placed in holder 13, and three exposures are made in sequence through the filters of the filter disc 16. The computer 10 uses the information from the modified image contained in frame store 23 to control the cathode ray tube 11 of the exposing unit and the other components of the exposing unit to expose the light sensitive paper 40 in such a manner that, after further processing in the conventional manner, the final image will have characteristics corresponding to the modified image which was displayed on the monitor 24. For example, the density of the image may be controlled by controlling the number of scans of the cathode ray tube used to illuminate the negative during the exposure. The colour balance may be controlled by controlling the relative number of scans which are used to illuminate the negative through each of the three filters of the filter mechanism 16. The contrast may be modified by increasing or decreasing the brightness of selected portions of the image appearing on the cathode ray tube 11, thereby to vary the density in selected portions of the final image. A similar process may be used to control colour saturation. The size and crop of the final image may be controlled by controlling the relative positions of the components of the exposing unit.

The exposing unit and monitoring unit may be part of a single apparatus, using a common computer. In that case, the scanning device 21 could be positioned, during the monitoring process, in the optical path of the exposing unit, at any point between the negative 30 and the position of the sensitive paper 40. For example, a photocell could be positioned in the optical path, the cathode ray tube 11 being used to sequentially illuminate portions of the original during scanning, three scans being made through respective filters of the filter disc 16. Alternatively, the exposing unit and monitoring unit could be provided .as separate apparatus. For example, the user could have the monitoring unit in his own premises, and the relevant data from the modified image could be recorded, for example on a computer disc which could then be sent together with the negative to a processing laboratory equipped with the appropriate exposing unit.

The computer controlling modification of the digitised image could be programmed to enable the image to be altered in other ways. For example, it could be programmed to enable local areas of the image to be specified by the user, for example using a mouse to define the edge of the area, and for various characteristics of the local area to be modified. The apparatus could be adapted to enable a form of photo-composition, as follows. Two or more originals are scanned in succession, the digitised images being stored separately. The computer is programmed to enable specified parts of the images to be. combined to form a single image, the image being displayed on the monitor screen and modified as required by the operator. During the exposing step, each original in turn is inserted into the exposing unit, the exposing display on the cathod ray tube or other display device being controlled so that only the appropriate parts of each original are exposed.

The apparatus could be arranged to enable extraneous spots or larger areas on the original to be corrected, in a manner analogous to the conventional techniques of spotting and rebrushing. The spots appearing on the monitor could be identified by the operator, for example using a mouse, so that information about the positions of the spots is inputted to the computer. After the main exposure through the original, the original could be removed and replaced by an opal screen, and an additional exposure made with the exposing display controlled so that the spots are exposed in such a manner as to mimick the surrounding image. A similar technique could be employed for larger areas.

The exposing unit of the invention can be adapted to operate in accordance with various conventional techniques. For example, the exposure could be made through red, green and blue filters as described ("additive" exposure) or through yellow, magenta and cyan filters ("substractive" exposure). In accordance with another aspect of the invention, the apparatus could be arranged so that an initial exposure, through each of the filters in turn, is made with a conventional "white" light source in place of the display device, to produce a "base" image. For example, the conventional light source could be permanently fixed in the exposing unit, with an arrangement of movable mirrors, driven under control of the computer, to introduce the light source into the optical path when required. A subsequent exposure is then made using the display device, to modify the eventual image as required, both exposures being carried out under control of the computer. Alternatively, an initial exposure can be made in white light, without the presence of filters (for example through a transparent portion, of the filter disc 16) , followed by an exposure using the display device .and filters, the two exposure stages being controlled to produce the required image, in a manner analogous to the conventional techniques of '.'additive top up" and "substractive termination".

The computer controlling the cathode ray tube or other display device during ____ exposing step is programmed to modify the digitised -image automatically to take into account the characteristics of the exposing apparatus and of the photographic paper or other medium on which the final image is to be formed, the necessary data about the medium being inputted into the computer at a suitable stage. Thus, where no modification of the original is required, the apparatus of this invention can be used to produce an exact reproduction of the original.

In the described apparatus, during the exposing stage, the photosensitive paper or other medium is exposed successively through the different colour filters. This enables the apparatus to be used to produce colour separations, for use in making printing plates for printing reproductions of the original. Thus, in the exposing stage, a separate black-and-white photosensitive sheet or other medium is exposed through each filter, to produce a separation for each of the colours. During each exposure, the cathode ray tube or other display device is controlled by the computer to provide each separation with appropriate cha acteristics.

Claims

1. A method of producing a photographic reproduction from an original bearing an image to be reproduced, comprising the steps of generating and storing a digitised image representative of the image on the original, displaying, the digitised image, modifying the digitised image thereby to modify the displayed image until it exhibits desired characteristics, and exposing a light sensitive carrier to light from a light source transmitted through or reflected from the original, the exposing step being carried out as a sequence of exposures in light of different colours, each exposure being controlled in dependence on information contained in the modified digitised image so that the reproduction obtained following the exposing step has characteristics corresponding to those of the displayed modified image.

2. The method as claimed in Claim 1, in which the light source is a display device arranged to display an image which, during each exposure of the exposing step, is projected onto the original.

3» The method as claimed in Claim 1 or Claim 2, in which the exposing step comprises exposing the light-sensitive carrier in sequence through different colour filters.

4. The method as claimed in any preceding claim, in which the light-sensitive carrier is exposed in sequence in light of three ^■complementary colours.

5. The method as claimed in any preceding claim, in which the step of generating and storing a digitised image comprises scanning the original sequentially in light of different colours respectively corresponding to, or complementary to, the colours employed in the sequential exposures of the exposing step.

6. The method as claimed in Claim 5t in which the original is scanned sequentially through different colour filters.

7^'. The method as claimed in any preceding claim, in which the exposing step is carried out at a location remote from that at which the steps of digitizing the.image and modifying the digitised image are carried out, information representing the modified digitised image being stored in a portable storage medium such as a computer disc which is transported,to the remote location.

8. The method-as claimed in any preceding claim, in which the exposing step includes making an initial exposure using a homogeneous light source in place of the controlled light source, and making subsequent exposures using the controlled light source.

9- Apparatus for producing a photographic reproduction from a photographic original bearing an image to be reproduced, comprising means for generating and storing a digitised image representative of the image on the original, display means for displaying the digitised image, processing means modifying the digitised image in response to a manual input, to enable an operator to modify the displayed image until it exhibits desired characteristics, means for sequentially exposing a light sensitive carrier to light of different colours from a light source transmitted through or reflected from the original, and means for controlling the exposure in dependence on information contained in the modified digitised image so that the reproduction obtained following the exposure has characteristics corresponding to those of the displayed modified image.