JPH03212642A - Formation of secondary photographic copy for printing - Google Patents

Abstract

PURPOSE:To make a secondary photographic copy free from crosslines and sharp by illuminating a halftone plate with a scattering light source and photographing the plate at specified magnification. CONSTITUTION:When a secondary photographic copy for printing is formed from a halftone plate, this plate is illuminated with a scattering light source and photographed on a photographic sensitive material with a camera for plate making at 0.14-0.32 magnification. In the case of >0.32 magnification, crosslines are clearly recorded and moire occurs. In the case of <0.14 magnification, the sharpness of an image is deteriorated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a method of producing a secondary photographic original for printing from a screen printing plate.

More specifically, we will discuss a method for creating a continuous-tone photographic original without halftone dots from a halftone plate.

[Prior Art] When printing a continuous tone photograph, etc., a photographic original plate with shading (hereinafter referred to as a "halftone printing plate") is usually created and printed. However, when producing prints of the same photograph or the same design in different sizes, or when the same printing is carried out at multiple printing shops, it is convenient to create a secondary photographic manuscript for printing from the first halftone plate created. . Especially when combining multiple manuscripts from a single screen plate using a layout scanner, it is cheaper to create a secondary photo original for printing from the first screen plate than to re-produce the same screen plate. , and convenient.

However, when a secondary photographic manuscript made from a screen printing plate in the usual manner is subjected to screen resolution again, ``moiré'' appears, making it unusable.

In order to prevent this "moiré" from appearing, when taking pictures with a camera from a half-tone plate, the lens aperture was extremely narrowed down to cause a diffraction phenomenon, thereby eliminating the half-tone pattern in the secondary manuscript. .

(Special Publication No. 61-56503, Japanese Patent Publication No. 56-1940)
[Problems to be Solved by the Invention] However, the above two methods have a problem in that although the mesh disappears, the sharpness of the image is impaired.

The present invention solves this problem and relates to a method for producing sharp secondary photographic originals without mesh.

[Means for Solving the Problems] The present invention provides a method in which, when printing from a screen plate onto a photographic light-sensitive material, the imaging magnification is set to 0.14 times or more and 0.32 times or less, and the screen plate is illuminated with a diffused light source. The above-mentioned problem was solved by taking pictures with

[Operation] When creating a secondary photographic original for printing that is virtually mesh-free using a B-2 mesh plate (515 mm x 728 m + a), a plate-making camera is used to transfer the mesh plate to a photographic light-sensitive material.
Photographs are taken at a magnification of 12x to 0.50x.

For example, using Fujichrome duplicating film and Dainippon Screen's rD-451-8 plate making camera, a half-tone plate was printed on a milky white acrylic plate with a thickness of 6 mm.
Fix it at the mm position, and use the Japan Optical Department Avonikkor rf=
Photographed at 480mm - F = 9J with the aperture set to n. In this case, the milky white acrylic plate plays the role of a diffused light source.

A close examination of the finished photographic images shows that those taken at a magnification of 0.32 or higher clearly show mesh patterns, and when used as secondary photographic manuscripts, "moiré" occurs.

On the other hand, in images taken at a magnification of 0.14 or less, the mesh is not visible at all, but the sharpness of the image is significantly impaired.

In addition, if the photograph was taken without using a milky white acrylic plate used in the photographing optical system, meshes would remain even if the photograph was taken at a double frame, 14 or less.

In order to create a sharp secondary photographic original without mesh from a halftone plate, the resolution performance (unit: It is preferable to select the optical system and photosensitive material so as to reduce the number of lines per length.

The figure below shows the photographic magnification obtained by combining the photographic magnification and the number of screen lines of the halftone plate, and at which the mesh virtually disappears without impairing the sharpness of the image.

↓A range where the mesh disappears and the sharpness is not impaired [Example B-2 size, 175 lines/inch decomposed mesh positive for lithography (
4 x 5 size photosensitive material (101, 6 x 127n) for yellow version, red version, eye version, and black version)
The magnification was set to 0.15, which satisfies (ym). The photosensitive material and optical system used were as follows: A black plate was fixed at the position of a milky white acrylic plate 60w, a yellow plate was superimposed and fixed on top of the black plate in perfect alignment, and exposed for 1 second using a blue filter.

Next, remove the yellow plate, overlap the red plate, and expose for 4 seconds using a green filter.Furthermore, change the red plate to an eye plate and use a red filter for 1
Exposure was made for 6 seconds.

A Fujichrome developing film exposed three times was developed in a conventional manner to obtain a secondary photographic manuscript.

When a lithographic halftone positive plate was again created and printed from this secondary photographic manuscript in the usual manner, a sharp printed matter with no moiré was obtained.

The embodiment described above is a method of directly creating a secondary manuscript for printing with a reversed color positive from a halftone positive for planography. Anything positive is fine.

In the case of a net negative, a positive photographic material (such as a print film) is used, but in the case of a net positive, a negative is made once using a negative photographic material instead of a duplicating film, and then the above-mentioned positive photographic material is used. You can also make a positive using .

In this case, you can erase the halftone dots by changing the magnification for negative exposure and positive exposure.

[Effects of the Invention] The present invention makes it possible to make the halftone pattern image of a halftone original or halftone printed matter projected onto a photographic light-sensitive material into a size that cannot be resolved by the photographic light-sensitive material by limiting the photographing magnification. This has the excellent effect of producing sharp continuous-tone secondary photographic originals for printing without halftone dot patterns.

Claims (1)

[Scope of Claims] In the preparation of a secondary photographic manuscript for printing from a screen printing plate, the imaging magnification when printing from the screen printing plate onto a photographic light-sensitive material is set to 0.14 times or more and 0.32 times or less, and a diffused light type. It is characterized by illuminating the printing plate with a light source and photographing it.
How to create a secondary photo manuscript for printing from an Amihara plate.