Gradation processing method and apparatus for radiation image recording system

An apparatus for processing the gradation of a radiation image in a radiation image recording system which comprises radiation image read-out means including scanning means for scanning a stimulable phosphor carrying a radiation image stored therein with a stimulating ray, a reading means for reading out the radiation image stored therein by detecting the light emitted from the stimulable phosphor upon stimulation thereof and converting the light to an electric signal having a level corresponding to the amount of the emitted light, a signal processing means for processing the electric signal, a modulating means controlled by the processed electric signal, and a recording means controlled by the modulating means for reproducing on a recording material an image corresponding to the radiation image recorded in the stimulable phosphor,

• said signal processing means comprising a signal converting means which converts the electric signal of the minimum level corresponding to the minimum amount of the light emitted from the stimulable phosphor to the level which results in the optical density in the image reproduced on the recording material within the range from the fog density of the recording material to the fog density plus 0.3 in terms of optical density, converts the electric signal of the maximum level corresponding to the maximum amount of the light emitted from the stimulable phosphor to the level which results in the optical density in the image reproduced on the recording material within the range from 1.5 to 2.8 in terms of optical density, and converts the electric signal of the level between the minimum level and the maximum level to a level which results in the optical density in the image reproduced on the recording material that monotonously increases as the level of the electric signal rises.