Polaroid SX70 manual Setting the exposure counter, Viewing and focusing

Gears in the front cover must engage the main gear train of the camera before the gear train is put into motion. A switch (S7) located in the forward section of the gear train compartment initiates the application of power to the gear train drive motor. Switch (S7) is actuated by two components

(1)A projection on the front cover latch (Figure 1-6 A), and

(2)A post on the right rear edge of the front cover (Figure 1-6 B).

front edge of the front cover. The camera is now ready to take the first picture.

4. Setting the exposure counter

When a used film pack is removed from the film chamber, the action automatically resets the exposure counter at the rear of the camera to the start position, closing S8. With a new film pack installed and the front cover closed and latched ( S7 closed), the motor is powered, and the dark slide is ejected. The exposure counter turns to number 10 (Figure 1-7), indicating that 10 pictures remain in the pack.

Figure 1-6 S7 contacts open and closed

Thus, the cover must be fulled closed, the gears engaged, and the latch fully seated, in order to actuate the drive motor.

As S7 closes, power is applied to the drive motor (S8 is also involved and is discussed in a following paragraph), the gear train is set in motion and actuates a device called the film pick. The pick engages the dark slide, pushes it into the spread rolls and the dark slide is ejected from the lower

Figure 1-7 Counter

5. Viewing and focusing

Viewing and focusing is accomplished through a reflect system (Figure 1-8 A). In the viewing mode the image passes through the lens to a fixed mirror which reflects it down to the Fresnel viewing screen. The viewing path from the viewfinder eyepiece lens is from a parabolic mirror and wafer lens, off the fixed mirror to the Fresnel screen. On most cameras the Fresnel screen contains a circular split-image aera which is used to focusing aid. A knurled knob (the focusing wheel) on the shutter housing is rotated to adjust the camera focus. The scene is in focus when a vertical line within the split-image aera is perfectly straight. On early cameras (without a split-image feature), the scene is in focus when the image seen on the Fresnel screen is sharpest.

6. Viewing and focusing

The exposure is made by pressing the release button. This completes the electrical circuit to the