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Sony SAL1870 Service Manual page 43

Lens for dslr camera
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4-4-2. Focus-shift/Flange Back (f'F) Adjustment
Equipment
• 1000 mm Collimator
• Flange Back Tester
• A-mount Attachment
• Flange Back Gauge (43.50mm)
• Adhesive bond (B-10)
1. Preparations
1) Remove the zoom rubber ring.
Fig.4-4-5
Adjusting Method
1) Turn the knob of the flange back tester, and set the dial gauge value to "46.48 mm" referring to "4-4-1. Focus-shift/Flange Back (f'F)
Check".
2) Set the zoom ring of the checking lens to Tele end position (focal length: 70 mm).
3) Loosen the two screws fixing the focus stopper, and turn the focus ring so that the chart image is the sharpest. (Refer to Fig.4-4-6.)
4) Set the focus stopper until it stops in arrow direction while holding the focus ring, and tighten the two screws. (Refer to Fig.4-4-6.)
Two screws
5) Set the zoom ring of the checking lens to Wide end position (focal length: 18 mm).
6) Turn the knob of the flange back tester until the chart image is the sharpest while looking through the microscope.
This flange back (f'F) is f'w.
7) Calculate focus error amount using the following formula.
Focus error amount = Flange back (f'w) reading - 44.72 mm
Focus error amount: Amount that should be adjusted by the back adjustment washer thickness.
f'w:
Flange back value (Reading value) at zoom ring is Wide end (focal length: 18 mm), and focus ring is position
of step 4).
SAL1870 (3.5-5.6/18-70) (DT 18-70mm F3.5-5.6)
Zoom Rubber Ring
Focus Ring
Set the focus stopper
until it stops in arrow direction.
Focus Stopper
Fig.4-4-6
4-14

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