Accurate control of the lateral position and spacing of a photosensitive medium (2) is provided for recording a succession of lines representing graphic images or portions thereof, without mechanical edge guides. The apparatus includes an optical edge detector (14), a film drive assembly having two independently controlled feed units (10; 12), and a deviation correction means to correct the position prior to actual printing of images. Preferably, a triang­ulation method is used to electronically correct the drive path of the medium (2). Error-correction is obtained by the combined action of the two independent feed units (10; 12) operated by an electronic control circuit receiving signals generated by the optical edge detector. The apparatus also includes means (35-37) to maintain the image receiving section of the photo­sensitive medium (2) in a flat plane. An image placement carriage (200) carrying optical elements (202) is supported on magnetic slider pads (211-213) forming bearing elements which hold the carriage onto smooth tracks (208) made of magnetic material, thus minimizing or eleminating vibrations from the motion of the carriage and improving the quality of the images formed on the photosensitive medium (2).