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Focus-Shift Check/Adjustment (Aperture) - Sony SAL135F18Z Service Manual

Lens for dslr camera (sonnar 1.8/135 za) (sonnar t* 135mm f1.8 za)
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Ver. 1.4 2007.12
The changed portions from
Ver. 1.3 are shown in blue.
4-5.

FOCUS-SHIFT CHECK/ADJUSTMENT (APERTURE)

This section describes the check/adjustment 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 77mm (SAL135F18Z)
1. Preparations
1) Perform "1. Preparations" of "4-4-1. Flange Back (f'F) Check".
2) Set the checking lens focus to the infinite.
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 77mm 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 77mm).
Focus-shift = Flange back (f'F) reading (using aberration measuring cap 77mm) - flange back (f'F) of open aperture reading
Specification
Focus-shift (mm) = – 0.05 to +0.13
4) Perform the "4-11. WRITE dSB".
SAL135F18Z (Sonnar 1.8/135 ZA) (Sonnar T
Aberration measuring cap 77mm (SAL135F18Z)
Fig.4-5-1
135mm F1.8 ZA)
*
4-26

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