To suppress fluctuation of the sensitivity of a developing solution to a minimum against changes in developing conditions while having a simple and inexpensive configuration of a developing unit in an automatic developing machine in a developing process of a photosensitive planographic printing plate precursor exposed along a high-resolution image.
The method for replenishing a replenisher in an automatic developing machine for a photosensitive planographic printing plate precursor is carried out by comparing a conductivity value of a developing solution obtained by measuring the conductivity of the developing solution with a preliminarily determined conductivity reference value and replenishing the developer with a developer replenisher when the conductivity of the developing solution is lower than the conductivity reference value. The conductivity reference value is changed in such a manner that: a preliminarily determined conductivity reference value optimal for a high-resolution image is used on processing a photosensitive planographic printing plate precursor exposed along a high-resolution image in which an output datum of 50% area ratio is ≥210 lines/inch in terms of a peripheral length of an image area in an image unit that constitutes a gradation of a screen image; and an ordinary reference is used for a printing plate precursor not having a high-resolution image.
Hironori Honda
Toshimitsu Ichikawa
Takeshi Takamatsu
Yuriko Hamada
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