Method of positioning mask using variable mask mechanism and variable mask mechanism

A method of positioning a mask using a variable mask mechanism capable of displacing the mask for partially blocking a light beam for exposing a photosensitive material when images on a negative film are exposed onto the photosensitive material and of changing an amount of opening of an aperture through which the light beam passes, said method comprising the step of:

• measuring a density of each image by a density measuring unit in a state in which the mask is in alignment with a range in which the density of each image on the negative film is measurable;
• temporarily shifting the mask to a position set as an origin;
• and
• thereafter displacing the mask to a range in which the images on the negative film are capable of being exposed, to change the amount of opening of the aperture, thereby exposing the photosensitive material provided on an optical path different from an optical path extending to the density measuring unit.

A variable mask mechanism capable of displacing a mask for partially blocking a light beam for exposing a photosensitive material when images on a negative film are exposed onto the photosensitive material and of changing an amount of opening of an aperture through which the light beam passes, comprising:

• a drive source for displacing the mask to change the amount of opening of the aperture;
• a sensor for detecting the mask to confirm a position of the mask;
• and
• a controller for controlling an operation of said drive source based on information sent from said sensor upon measuring a density of each image so as to align the mask with a range in which the density of each image on the negative film is measurable and for controlling the operation of said drive source based on the information to shift the mask to a range in which the images on the negative film are capable of being exposed, upon printing/exposing the photosensitive material, thereby changing the amount of opening of the aperture.