Polaroid SX70 manual Fresnel Figures 2-3 a and 2-3 B, Viewfinder optics exposing

Page 16

Figure 2-2 Viewfinder optics (exposing)

the subject passes through the camera lens and is reflected by the viewing mirror (on the inside surface of the mirror cover) to the Fresnel viewing screen.

The entire subject image is now reproduced on the viewing screen. At this point, viewfinder optics must be employed for focusing. The optics must transfer the image from the viewing screen to the eye (done by the parabolic mirror and the viewing mirror) and must present the image in a fairly sharp contrast to permit proper focusing (done by the eye lens and parabolic miror).

1. Fresnel (Figures 2-3 A and 2-3 B)

The special Fresnel (pronouced Freh-nell) screen is employed to enhance the viewing image by increasing the brightness and defintion. If a matte white surface were substituted for the Fresnel screen, an image would still be visible. However, the light rays striking nearest the corners of the screen meet the screen at a more oblique angle than the rays striking near the center. At this greater angle, a larger percentage of the light is dispersed and less light is returned to the viewer. Thus, on a matte-screen image the corners would appear darken than the center. The Fresnel screen is designed to overcome this problem.

Image 16
Contents Page Page Description General DescriptionCamera Operation Opening the CameraLoading the Film pack Starting the Automatic MechanismSetting the exposure counter Viewing and focusingViewing and shooting Completing the film pack Exposures using flashDeveloping the print Shutter Description Ambient Light Mode Closing the camera11 a Location & Arrangement of internal parts Shutter Description Flash Mode Page 14 S5 being opened by the recock ram Gear train Page Power Source IntroductionLens Viewing and Exposing SystemFresnel Figures 2-3 a and 2-3 B Viewfinder optics exposingFresnel screen Viewfinder MirrorsFlare baffle Camera Elctronics 1. GeneralSwitch functions SX-70 Switch locationsS3 Being opened by recock ram S4 Switch operating configurations Switch Function Table Function SequencePage Flash Timing Sequence Chart Shutter Mechanical Details Figure Shutter, exploded viewA Solenoid S2 operation Film Processing Components Sequence of OperationsPage Max III Troubleshooting Introduction Initial TestsSX-70 Cmaera Repair Inspection Procedure Power supply and pack simulator Figure Test Equipment OperationCollimator Figure Location of new collimator targetDisengaging the idler gear Comprehensive Testers -6 Comprehensive testerModel B Camera tester Model B Camera Tester Comparalumen Light Levels Table Light Leak Tester FigureFlash Simulator Board Figure Light leak test systemManual Function Tester Figure 10 Manual camera testerManual Function Test Sequence Optical System Exit Pupil TestEntrance Pupil Test 13 Aligning the exit pupil gageUSE of Analysis Charts Concave Mirror Distortion CheckFresnel Quality Check Collimation16 Fresnel standards chart Camera/Shutter Isolation 18 Flex circuit terminal locationsCamera Analysis Charts 19 Test points on SX-70 shuttersPage Installation Front COVER/SPREAD Roll AssemblyRemoval Repairs / Adjsutments Loose Front Covers Front cover hinge studsBending the stop latch Top Spread Roll Looseness Interference Between Front and Bottom CoversReplacing the Light Shield Cam Mirror Cover / Boot Assembly Front cover light shield camBoot retaining screws