just before the film advance cycle an electro magnetic solenoid 65 attached to the film pressure plate 55 is automatically energised which retracts the film pressure plate 55 and withdraws the sprocket pins 54 allowing the film 60 to wind on the required distance upon completion of the film advance cycle the electro magnetic solenoid 65 is de energised bringing the film pressure plate 55 back to its normally engaged position and the sprocket pins 54 are again holding the film 60 in perfect alignment through the film sprocket holes in operation the camera operator wishing to make a master grid of 48 images for further mass duplication prepares the required number of slides in proper sequence after setting the field size and focusing through the reflex finder he proceeds to expose the master on a special high resolution colour copy film as follows upon pressing the 34 expose advance 34 button 70 see fig1 the shutter opens withdrawing the 45 u00b0 mirror mounted on its back and allowing the image rays from the lens to traverse the aperture to the film the shutter at the 34 open 34 end of its travel contacts a micro switch which activates the electronic flash exposing the image and the shutter then closes upon closing the shutter contacts a second micro switch which activates a motor that causes the helical programmer to make one turn causing the sliding carriage to move to the right the proper distance changing slides and making successive exposures up to no 6 bring the sliding carriage to the limit of its movement and the helix to its 34 dwell 34 position at this point a limit micro switch causes a second motor to wind the film forward and after photo no.