Calibrating The B-600 Tester - Polaroid 636 Repair Manual

D. Calibrating the B-600 Tester
Calibration of the B-600 Tester is done in three steps:
(1) calibrating the Light Source,
(2) the Horn and
(3) the Electronics Unit.
While the probability of the B-600 going out of calibration is unlikely, the B-600 should be
checked daily.
Calibrating the B-600 Light Source
Light Source calibration is done using a 640 Master Camera, which measures light levels in
both the visible and infrared regions.
Two switches are located on the top of the Camera: Motor ON/OFF prevents the Camera from
cycling while it is used as a light level standard, and Meter ON/OFF controls the meter on the
back of the Camera. A slide on the front of the Camera, next to the lens, controls the blade
opening.
Calibration procedure:
1. Turn ON the light source and let it warm up for 30 minutes.
2. Slide the Master Camera on the horn with the motor switch OFF and the meter switch ON.
3. Place the Master Camera in front of the Light Source window. Set the light level for
100 cd/sq. ft.
4. Slide the blade control all the way to the left (as viewed from the back of the Camera) until
you hear a click. This signals the blades have unlatched.
5. Slide the blade control all the way to the right: this is the blade position at which the
standard camera is indicating the visible light level. Since the standard camera is a direct
reading device, the meter reading is the actual light level.
6. Tilt the camera and the horn back so that the shutter blades can be seen through the taking
lens.
7. Slide the blade control to the left until the shutter is at full aperture: this is the point at
which the camera will indicate the IR light level.
8. Place the camera back in front of the Light Source: the meter reading should be 3.5 to 4
times the visible mode reading. (Ideally, the visible reading should be 100 and the IR
reading 350 to 400.)
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