Polaroid Joshua Vision Service Manual page 25

Figure 1-18. Joshua Blade Position Encoder System
Ambient Visible and IR levels are measured by a dual- photocell Photometer on the PC board, through
green and black lenses on the lens mounting plate and corresponding apertures in the shutter blades. Each of
these exposure components — ambient and IR — is individually integrated (electronically summed) by its
own integrator.
The Two-Zone Focus System uses, under microprocessor control, the main three-element Taking Lens
only, for near zone (0.6 to 2.7 m or 2 to 9 ft.) exposures — or the main Lens plus the automatically-
positioned Far Focus Lens for exposures between 2.7 m (9 ft.) and infinity (Figure 1-19).
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