PURPOSE: To use a master image which is not transparent to radiation by controlling the transmittance of a medium having a variable transparency to form an alternative image which is transparent to radiation.

CONSTITUTION: A member 25 which has a high resolution and is divided into many picture elements or bands is so designed that the transmittance or each picture element is modulated or controlled independently of other picture elements. Information related to the master image which reaches the member 5 from a running unit 1 or another signal source 3 is reproduced on the member 5 by selective control of transmittance of individual picture elements. The member 5 generates an alternative to the master image which is transparent to light in this manner. Light emitted from a light source 6 passes the member 5 and exposes a photographic material 8 to printing in a proper form. In this case, the transmittance of each picture element of the member 5 is modulated in accordance with information related to the master image, and it is transferred to the photographic material 8 by light of the light source 6.