Process for producing pre-press color proofs

• US 4,553,835 A
• Filed: 06/29/1984
• Issued: 11/19/1985
• Est. Priority Date: 02/11/1982
• Status: Expired due to Fees

• Current Assignee: James T. Morgan Jr
• Original Assignee: James T. Morgan Jr
• Inventors: Morgan, James T. Jr.
• Primary Examiner(s): WINTERCORN, RICHARD
• Application Number:
  US06/626,134
• Time in Patent Office: 508 Days
• Field of Search: 355/32, 355/35, 355/132, 355/77, 355/71, 355/88, 358/299, 358/302
• US Class Current: 355/77
• CPC Class Codes: G03F 3/107 using silver halide photosensitive materials

Abstract

A process is disclosed for preparing a pre-press proof of an original subject having highlight, midtone and shadow tone areas using a color print paper wherein the dyes of the print paper are brought into substantial color compliance with the yellow, cyan and magenta process inks to be used in producing a lithographic reproduction of the original subject. The tonal range of the proof image is also extended to closely match that of the final printed product. After determining the densitometer readings for yellow, magenta and cyan through blue, green and red filters respectively for the print paper and the process inks, the print paper is exposed to light through each filter with an appropriate color separation halftone negative over the film and with combinations of filters being used for hue correction of the yellow, magenta and cyan film dye coupling dyes. A masked short scale yellow separation halftone negative is used to prepare a dye transfer matrix thereof, the image defining portions of tee matrix are dyed with a yellow transfer dye and the yellow is then transferred to the print paper sheet since the yellow coupling dye of the print paper has an excess of magenta and will not provide a true lemon-yellow color in the proof. Exposure of the print paper through color separation positives along with the same separation negatives through corresponding filters provides tone balance and allows compensation for dot gain in printing.

Claims

1. A method of preparing a pre-press proof of an original subject having highlight, midtone and shadow tone areas using color print paper wherein the dyes of the print paper have been brought into substantial color compliance with the yellow, cyan and magenta process inks to be used in producing a lithographic reproduction of said original subject, and the tonal range of the proof image has been extended to closely match that of the final process ink print, said method comprising the steps of:

preparing yellow, cyan and magenta color half tone separation negatives and positives of the original subject to be reproduced;

separately placing the halftone negatives in sequential order over a sheet of color print paper sensitive to green, blue and red light respectively;

exposing the print paper sheet to light passed through a blue filter when the yellow halftone separation negative is over the print paper sheet, a red filter when the cyan halftone separation negative is over the print paper sheet, and a green filter when the magenta halftone separation negative is in place thereover,

said exposure of the print paper sheet being carried out with each halftone separation negative in place over the print paper sheet for a predetermined time period sufficient to cause the dyes of the print paper sheet upon development thereof to exhibit densitometer readings wherein through a blue filter, the yellow reading of the exposed print paper relatively closely matches the yellow reading obtained by densitometer measurement through a blue filter of the yellow process ink, through a green filter the magenta reading of the exposed print paper relatively closely matches the magenta reading obtained by densitometer measurement through a green filter of the magenta process ink, and through a red filter the cyan reading of the exposed print paper relatively closely matches the cyan reading obtained by densitometer measurement through a red filter of the cyan process ink;

during exposure of the print paper sheet to light through a red filter while the cyan halftone separation negative is over the print paper sheet, also exposing the print paper sheet to light through a green filter for a sufficient period of time to cause the dyes of the print paper sheet upon development thereof to exhibit a densitometer reading wherein the magenta reading through a green filter relatively closely matches the magenta contaminant reading obtained by densitometer measurement through a green filter of the cyan process ink,

during exposure of the print paper sheet to light through a green filter while the magenta halftone separation negative is in place over the print paper sheet, also exposing the print paper sheet to light through a blue filter for a sufficient period of time to cause the dyes of the print paper sheet upon development thereof to exhibit a densitometer reading wherein the yellow reading through a blue filter relatively closely matches the yellow contaminant reading obtained by densitometer measurement through a blue filter of the magenta process ink; and

increasing the tonal range of the color print paper proof by also placing on the print paper sheet when the magenta separation halftone negative is associated therewith, the magenta halftone separation positive, and the yellow halftone separation positive on the print paper sheet when the yellow halftone separation negative is associated with the print paper sheet, and the cyan halftone separation negative on the print paper sheet with the cyan separation halftone positive, and in each instance passing additional light through the red, green and blue filters respectively for time periods sufficient to progressively extend the tonal range of the highlight and midtone areas of the film proof without unduly affecting the shadow tone area thereof.

2. A method as set forth in claim 1, wherein is included the steps of passing light through the red and green filters while the cyan halftone negative and the cyan halftone positive and the magenta halftone negative and magenta halftone positive respectively are on the print paper sheet for a longer period of time than light is passed through the blue filter while the yellow halftone negative and yellow halftone positive are on the print paper sheet.

3. A method as set forth in claim 2, wherein said longer time period is approximately two to four times the exposure time period through the yellow halftone negative and yellow halftone positive on the print paper sheet.

4. A method as set forth in claim 1, wherein is included the steps of preparing a halftone color separation negative for a selected one of the process inks which is of shorter scale than the first mentioned half tone separation negative of such process ink, using the short scale and negative to prepare a dye transfer matrix thereof, dyeing the image defining portions of the matrix a color corresponding to the selected process ink, and transferring the dye on the matrix to the print paper sheet after development thereof.

5. A method as set forth in claim 4, wherein is included the steps of preparing at least two separate short scale half tone negatives of different process inks, using such negatives to prepare separate dye transfer matrices thereof, dyeing the image defining portions of the matrix colors corresponding to the selected process inks respectively, and successively transferring the dyes on said matrices to the print paper sheet after development thereof.

6. A method as set forth in claim 4, wherein said step of preparing the short scale halftone separation negative includes enhancing and increasing the tone detail of the highlight and midtone portion of the scale without substantially disturbing the shadow portion of such scale.

7. A method as set forth in claim 4, wherein said step of preparing the short scale halftone separation negative includes subjecting the original work to color separation on an electronic scanner with the highlight setting thereof being established at a value of at least about 66%.

8. A method as set forth in claim 4, wherein said step of preparing the short scale halftone separation negative includes subjecting the original work to color separation on an electronic scanner with the highlight setting thereof being established at a value of about 75% to 80%.

9. A method as set forth in claim 7, wherein said scanning is carried out with the shadow setting thereof at its normal value.

10. A method as set forth in claim 4, wherein said step of preparing the short scale halftone separation negative includes placing a clear spacer sheet over a layer of light sensitive film disposing a full scale halftone separation positive of the halftone separation negative of said selected process ink over the spacer and overexposing the film to an extent to decrease the highlight and midtone area detail while enhancing the shadow tone detail.

11. A method of preparing a pre-press proof of an original subject using color print paper wherein the dyes of the print paper have been brought into substantial color compliance with the yellow, cyan and magenta process inks to be used in producing a lithographic reproduction of said original subject, said method comprising the steps of:

exposing the print paper to light through blue, green and red filters for times correlated to cause the print paper to exhibit densitometer readings for yellow, cyan and magenta through respective filters which substantially correspond to densitometer readings for the yellow, cyan and magenta process inks to be used in reproduction of the original subject through each of said filters;

preparing a short scale halftone color separation negative of at least a selected one of the process colors;

using the short scale halftone negative to prepare a dye transfer mix therefrom;

dyeing the image defining portions of the matrix with a transfer dye having a color corresponding to the selected process ink; and

transferring the dye on the matrix to the color print paper after the development of such paper.

12. A method as set forth in claim 11, wherein said step of preparing a short scale halftone separation negative includes masking the image reproduced on a graduated scale basis with a greater proportion of the shadow tone areas being masked than that of the highlight areas.