4-5. FOCUS-SHIFT CHECK/ADJUSTMENT (APERTURE (AMOUNT OF SPHERICAL ABERRATION))
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 55mm (SAL35F14G)
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 55mm (F8 equivalent) on the tip of lens as shown in the Fig.4-5-1, then measure the flange back (f’F).
Aberration measuring cap 55mm (SAL35F14G)
Fig.4-5-1
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 to +0.15
4)Perform the “4-9. WRITE dSB”.
SAL35F14G (1.4/35G) (35mm F1.4G)
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