Polaroid SX70 manual Completing the film pack, Developing the print, Exposures using flash

The image is reflected by the mirror onto the film surface. the electronic metering system determinesthe required exposure, and programs the shutter opening and duration accordingly.

The incorporation of a mirror in tghe lens-to-film path necessitated by the nature of the film. No separate negative film is employed. Instead, the image appears as a direct positive. Since the final product is an opaque print, it is viewed by reflection. As a result, the mirror is needed to reverse the image so that the final print will be properly oriented. This requirement, in turn, dictates the use of the reflectance type viewing screen rather than a ground-glass type transmission system.

Note that the film surface is deplaced from the Fresnel viewing screen by the thickness of the viewing screen assembly. The correct focal distance for both viewing and exposure is properly maintened, however, since the surface- coated exposure mirror is deplaced by the same dimension.

During exposure, the light from the viewing system must be prevented from striking the film. This is accomplished by a rubber light stop adhered to the hinged Fresnel carrier. When the Fresnel carrier moves upward, the light stop blocks off light from the viewfinder eyepiece.

As indicated by the foregoing description, the viewing system is blacked out during the actual exposure.

As soon as the exposure is complete the mechanism returns the viewing screen to its initial position and the picks feeds the exposed film to the spreader rolls. The rolls break the pod, spread the developer, and eject the film from the camera.

7. Completing the film pack

As each exposure is completed, the exposure counter substracts one digit until the 10 exposures have be made. The counter then indicates 0...

When this occurs, switch S9 is closed. Closing this switch inhibits the flash and the exposure timing. Since the counting cycle is initiated by the insertion of a film pack, the pack may not necessary contain a full supply of film. If, for some reason, a partially used pack is removed and reinserted, the top film will be the dark

slide. The counter will start at number 10. Since switches S8 and S9 are physically attached to the counter, the camera will cycle through 10 exposures even though there be less than 10 sheets of film in the pack. This deviation must be recognized whenever a partially exposed pack is used.

8. Developing the print

As in orther Polaroid pack cameras, the picture is developed ouside the camera. Unlike previous Polaroid Land Cameras, however, there is no negative to pell off and discard.

9. Exposures using flash

The SX-70 accepts a special 10-lamp flash bar that plugs into a receptacle directly over the camera lens. There are five lamps in a rowon either side of the bar which must be removed, rotated and reinserted after the fifth lamp has been fired (Figure 1-9).

Insering a flash into the flash socket closes switch S2 in the socket. This action sets up the shutter electronic circuit to permet firing of the flash lamp. A follow-focus mechanism, coupled to the lens focusing system arrests the shutter blades at an opening related to camera-to-suject distance.

NOTE : On early camera models, the light measuring circuit remains active even with the flash bar inserted into the socket. If the circuit determines that there sufficient ambient light, an exposure will be made without the flash. Cameras with «P» configuration or later shutters, do not have this light measuring feature in the flash mode. Regardless of the ambient light level, the circuits will fire the flash when a flash bar is in the socket (unless of course, the lamps have all been used).

If the array has been exhausted, the shutter will complete the exposure cycle without flash. Maximum exposure duration is 30 seconds.

When the exposure counter reaches 0 (empty) the camera will not fire a flash lamp even though unused lamps remain in the bar. The previously discussed deviation associated with the exposure counter is applicable to the flash functions. If an unusedlamp is in position and if a partially empty film pack has been reinserted, the camera will continue to fire lamps after the last sheet of film has been exposed, until the counter reaches 0.