Abstract: The apparatus comprises a principal light source, condenser, lenses, object and image planes movable with respect to one another and an auxiliary light exposure source. The condenser is constituted by two thin stepped lenses between which is arranged a corrector screen for the variations in illumination in the image plane due to the inclination of the useful beam to the axis of the system. This screen operates perpendicularly to its surface, the constituent elements of the source, of the condenser and of the pupil of the lenses used being fixed with respect to one another and movable in a single unit relative to the document to be reproduced according to the focal length of said lens determining the size of the document. The apparatus is useful for the reproduction of transparent documents in black and white or in color.