Focus-Shift Check - Sony SAL100M28 Service Manual

4-5.

FOCUS-SHIFT CHECK

This section describes the check of focus-shift amount resulting change of focal-length by aperture setting.
Equipment
• 1000 mm Collimator
• Flange Back Tester
• A-mount Attachment
• Flange Back Gauge (43.50mm)
• Aberration Measuring Cap 55mm
1. Preparations
1) Perform "1. Preparations" of "4-4-1. Flange Back (f'F) Check".
2. Checking Method
1) Set the lens aperture to the open aperture position, and measure the flange back (f'F).
2) Set the aberration measuring cap 55mm (F8 equivalent) on the tip of lens as shown in the Fig.4-5-1, then measure the flange back
(f'F).
3) Calculate amount of focus-shift using the following formula, and check that the specification is satisfied.
Note:
The focus-shift amount of the checking lens is difference between the flange back (f'F) of open aperture and flange back
(f'F) reading (using aberration measuring cap 55mm).
Focus-shift = flange back (f'F) of open aperture reading - flange back (f'F) reading (using aberration measuring cap 55mm)
Specification
Focus-shift (mm) = –0.06 to +0.08
4) When the focus-shift is out of specification, perform the parts replacement and adjustment/check referring to the Fig.4-5-2.
Replace the 3 group lens block
4-4. FLANGE BACK (f'F)
CHECK/ADJUSTMENT
4-5. FOCUS-SHIFT CHECK
OK
END
SAL100M28 (MACRO 2.8/100) (100mm F2.8 Macro)
Aberration measuring cap 55mm
Fig.4-5-1
Replace the G6 lens
4-4. FLANGE BACK (f'F)
CHECK/ADJUSTMENT
NG
4-5. FOCUS-SHIFT CHECK
NG
OK
END
Fig.4-5-2
4-14
Replace the G5 frame lens block
4-4. FLANGE BACK (f'F)
CHECK/ADJUSTMENT
4-5. FOCUS-SHIFT CHECK
OK
END