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

摘要

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 and of changing the amount of opening of an aperture through which the light beam passes, is provided which comprises the steps of measuring the density of each of images on a negative film in a state in which the mask is in alignment with a range in which the density of each image can be measured and thereafter shifting the mask to a range in which the images on the negative film can be exposed, thereby exposing the photosensitive material. Therefore, a position permissible range of the mask at the time of photometry and exposure is expanded. It is thus unnecessary to position the mask with accuracy higher than required. Further, the manufacturing cost of the variable mask mechanism can be reduced.