PURPOSE: To increase the density of the stripe filter and to improve the gradation reproducibility and resolving power of a color image by varying the transmissivity of the strip filter by using a mesh contact screen for plate making.

CONSTITUTION: The mesh separation contact screen 11 for plate making is superposed on a reversal film 10 and a mask 12 for exposure which have opening bored in (1:3) pitch proportion to the screen 11 is further superposed thereupon; and the reversal film 10 is exposed to red light while moved at an equal speed as shown by an arrow Y. Then, the exposure mask 12 is shifted by one pitch as shown by an arrow X and the reversal film 10 is exposed to green light while moved as shown by the arrow Y. Further, the exposure mask 12 is shifted by one pitch and the film is exposed to blue violet light and a specific developing process is carried out thereafter. This manufactured strip filter improves the picture quality of the color image.