Photomechanical process contains a process to convert an original of continuous gradation into dot images. In this process, there has been used an infectious developing technique as a technique that enables image reproduction with ultrahard gradation.
Lith-type silver halide photographic light-sensitive materials to be developed with the infectious development comprise a silver-chloride-rich silver chlorobromide emulsion containing at least 50 mol % of silver chloride and grains of which have a uniform shape and a narrow grain size distribution with an average value, for example, of 0.2 .mu.m. When these lith-type silver halide photographic light-sensitive materials are processed with an alkaline hydroquinone developer of low sulfite ion concentration, a so-called lith-type developer, images of high contrast, high sharpness and high resolution can be obtained.
The lith-type developer, however, is poor in preservability for its liability to air oxidation. And this makes it difficult to keep the developing quality constant even in a continuous processing.
There is known in the art methods to obtain high contrast images rapidly without use of the lith-type developer. For example, Japanese Pat. O.P.I. Pub. No. 106244/1981 discloses the use of hydrazine derivatives in a silver halide light-sensitive materials. According to these methods, contrasty images can be obtained by processing light-sensitive materials with a developer high in preservability and capable of rapid-processing.
In these techniques, however, the pH of a developer must be higher than 11.0 in order to heighten the hydrazine derivatives' high contrast providing capability. In such a developer with a pH value higher than 11.0, the developing agent is liable to be oxidized. Though the developer is not so unstable as the lith-type developer, oxidation of a developing agent often hinders formation of ultrahard images.
As measures to correct such a defect, there are disclosed silver halide photographic light-sensitive materials containing contrast improving agents workable even in developers of relatively low pH values in Japanese Pat. O.P.I. Pub. No. 29751/1988 and European Pat. Nos. 333,435, 345,025.
However, even when such light-sensitive materials containing contrast improving agents are developed at a pH less than 11.0, the gradation is still insufficient and an adequate dot quality cannot be obtained.