partial pack : the top of the sheet of film would be ejected as a dark slide and the counter would registrer «10». After the last actual sheet is used, the camera would still function until «0» is reached. If a flash bar were attached, and an unused bulb was available after the last film sheet was used, attempting to make another exposure would fire the flash.
The difference in the flash mode are :
inserting a flash bar closes S2, which activates solenoid #2 to move the interceptor into position. This controls the shutter blades according to focusing : the closer the subject the more light from the flash will bounce back. Therefore, the smaller the permitted aperture.
At the end of the «Y» delay, a flash delay circuit is activated, and when S4 switches from CB to CA, Ca sends power to the flash circuit. During the fixed flash delay, the photocell and S/T are operative , so that if enough light energy is collected before the end of the flash delay, the blades will be closed as in ambient picture. However, on newer cameras («P» configuration shutters), the flash will fire whether or not sufficient ambient light si available.
At the end of the flash delay (the blades at this point are open to the aperture dictated by focusing) power is removed from solenoid #2 and the discharge (flyback voltage) triggers the flash circuit, firing the flash and starting the flash time out interval (the fixed exposure time). If, on early cameras, an ambient exposure has been made,
At the end of the flash time out, the circuitry energizes solenoid #1 which closes the blades. if no flash has occured, caused by all the bulbs having been used, no signal will be sent to solenoid #1, and on early cameras an ambient exposure will be made. If the S/T has not collected sufficient light energy at the end of a fixed period (20 seconds), the blades will automatically close. On newer cameras, the exposure time remains short and a black picture will result.