Sony SAL20F28 Service Manual ▷ View online
4-5
SAL20F28 (2.8/20) (20mm F2.8)
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2. Checking of Image
Note:
Check the image of both master lens and checking lens.
1)
Start the Color Calculator 2.
Fig.4-2-3
2)
Read the image from the file menu.
Fig.4-2-4
3)
Set the Color Calculator 2 as follows.
Measured value display (Display menu): RGB+L*a*b*
Measuring method (Display menu):
Center Single Area
Fig.4-2-5
Color space (Edit menu): sRGB
Fig.4-2-6
Area size for calculate (Edit menu
→Option): 256×256 Pixels
Fig.4-2-7
4-6
SAL20F28 (2.8/20) (20mm F2.8)
4)
Click the calculate button to measure the image.
5)
After measuring, check the “G” values.
Average “G” value of the three images shoot with master lens:
(a)
Average “G” value of the three images shoot with checking lens: (b)
Fig.4-2-8
3. Checking Method
1)
Calculate aperture error using the following formula, and check that the aperture error is within the specification.
Aperture error = Average “G” value of checking lens (b) - Average “G” value of master lens (a)
Specification
Aperture error = –30
±5
2)
When the aperture error is out of specification, perform “4-2-2. Aperture Diameter Adjustment”.
Calculate button
Check the “G” value
Ver. 1.3 2008.01
The changed portions from
Ver. 1.2 are shown in blue.
Ver. 1.2 are shown in blue.
4-7
SAL20F28 (2.8/20) (20mm F2.8)
4-2-2. Aperture Diameter Adjustment
Equipment
• Luminance Box
• Camera DSLR-A100
• AE Master Lens
• Compact Flash (CF) Card (For image saving)
• Personal Computer (PC)
(Color Calculator 2 installed)
• Adhesive bond (B-10)
• Name ring wrench (72mm)
1. Adjustment Method
1)
Disassemble or assemble the checking lens into the state of Fig.4-2-9.
Fig.4-2-9
2)
Remove the adhesive bond fixing the iris aperture unit holding spring.
Fig.4-2-10
2nd Lens Block
Front Lens Barrel
1st Lens Block
Decoration Ring
Adhesive bond(B-10)(3 areas)
Adhesive Bond
Aperture Unit Holding Spring
Adhesive Bond
Iris Retainer Ring
Ver 1.2 2007.05
4-8
SAL20F28 (2.8/20) (20mm F2.8)
3)
Move the preset lever to set the preset ring at the open aperture position.
Fig.4-2-11
4)
Turn the aperture unit holding ring to adjust the position that the aperture blades are hidden into the edge completely.
Fig.4-2-12
5)
After the adjustment is completed, apply the adhesive bond (B-10) as shown in the Fig.4-2-13.
Fig.4-2-13
6)
Assemble the lens completely.
7)
Perform “4-2-1. Aperture Diameter Check”, and repeat “4-2-1. Aperture Diameter Check” and “4-2-2. Aperture Diameter Adjust-
ment” until the aperture error is within the specification.
Set the preset ring at the open aperture position.
Preset lever
Aperture Unit Holding RIng
Aperture blades are hidden into
the edge competely.
the edge competely.
Apply adhesive bond(B-10)(3 areas)
Bond
Aperture Unit
Holding Spring
Holding Spring
Bond
Aperture Unit
Holding Ring
Holding Ring
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