PURPOSE: To find the conditions of density-range compression and gamma correction rapidly, by irradiating a photographic film with light over a wide range including the lighting spot of the photographic film while superposing it with a light beam for spot lighting sequentially.

CONSTITUTION: Films 3, 3... are fitted in the windows 2, 2... of a rotary cylinder 1 and light sources 23 and 49 are turned on, some area of the film 3 is lit uniformly with a light beam from the light source 49 to project at enlarged picture on a screen 31 while a light spot is formed in its center. Then, the cylinder 1 is moved to align the spot to the lightest part found in the picture, and a photometric device 35 measures the lightness of the part. The light source 49 is turned off, the spot is aligned to the upper edge of the upper window 3, and motors 12 and 21 are put in operation, allowing a light beam spot from the light source 23 to scan the films 3, 3... horizontally at a high speed and vertically at a low speed. At this time, the density distribution of each primary color on each film is known from the outputs of the device 35 and a rotary encoder 20, and data required for the compression of a density area and gamma correction are obtained.