PURPOSE: To faithfully reproduce each color of a color original picture, and to correct an offset drift of a color film testing device, by correcting the offset drift in a state that a color balance is held satisfactorily.

CONSTITUTION: A shutter 15 is provided on a light control part 11 of a color film testing device, a color negative film 18 is irradiated by a light source 10, an image of a frame 18a is brought to an image pickup by a color TV camera 20, and it is displayed on a color monitor 35. This signal which has been brought to an image pickup is A/D-converted 22W24, and brought to a logarithmic conversion by look-up tables 25W27 for green, blue and red. This outputted density signal is sent to a color correcting circuit 28, and by a color correcting system of three lines and three rows, a difference of the spectral sensitivity of photographic paper and the camera is corrected. Each density signal which has been corrected in this way is brought to a negative/positive conversion and converted to a gradation corresponding to a characteristic curve of the photographic paper by gradation converting look-up tables 29W31. Each circuit thereof is controlled by a timing of a timing generating part 38 by a CPU 41.