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SAL2875 (2.8/28-75 SAM) (28-75mm F2.8 SAM)

4-4

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)

 

Calculate button

Check the “G” value

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) 

 

Aperture error = -30 to +10 (WIDE end: 28 mm)

2)  When the aperture error is out of specification, perform  4-2-2. Aperture Diameter Adjustment .

Adhesive bond (B-10)

1. Preparations
1)  Remove the rear light shield barrel.
2)  Set the zoom ring at the WIDE end position.
3)  Move the preset lever to set the preset ring at the open aperture position.

Rear Light Shield Barrel

Open aperture
position

•

2. Adjusting Method
1)  Loosen a little two screws and move them right and left so that the preset lever of the preset ring can be moved right and left.
2)  Set the zoom to TELE end (75 mm), move the two screws while seeing the lights from the rear lens element side, and tighten 

two screws at the position in which aperture blades are not hidden a little for the adjacent frame.

Two screws

Apply the adhesive
bond (B-10)

3) Perform 4-2-1. Aperture Diameter Check , and repeat steps 1) to 2) until the aperture error is within the specification.
4)  After finishing the adjustment, apply the bond (B-10) to the heads of two screws tightened in step 2).

Setting of the Flange Back (f F) measuring instrument.

1000 mm Collimator
Flange Back Tester
A-mount Attachment
Flange Back Gauge (43.50 mm)
Adhesive bond (B-110)

1)  Set the equipment as shown in the Fig. 4-3-1.

 

Flange back gauge (43.50 mm)

A-mount attachment

Objective lens (10x)

Dial Gauge (Min. scale: 0.01 mm)

Scale ring

Eyepiece lens (7x)

Eyepiece ring

•
•
•
•
•

SAL2875 (2.8/28-75 SAM) (28-75mm F2.8 SAM)

4-5

2)  Looking through the eyepiece lens, turn the eyepiece ring of the flange back tester so that cross line or scale in the view is the 

sharpest.

3)  Attach the flange back gauge (43.50 mm) securely to the A-mount attachment and hold them together.
4)  Turn the focusing knob of the flange back tester so that fine scratches on the flange back gauge (43.50 mm) is the sharpest.

Turn the knob in the direction of the arrow of Fig. 4-3-2 for correct reading.

 

Focusing knob

Focus on fine lines on the surface.

Always turn the knob in the arrow
direction for correct reading.

5)  Turn the scale ring of the dial gauge until the long pointer indicates  0 .

This position is the flange back (f F) = 43.50 mm.

 

Memorize the position of short-pointer.

1)  Attach the checking lens to the flange back tester, and set the 1000 mm collimator.

 

1000 mm collimator

Checking lens

2)  Set the focus ring of the checking lens to 

∞

 (infinity) index or near 

∞

 (infinity)  and adjust the optical axis, observing the 

microscope so that the chart can be seen in the center.

3)  Turn the focusing knob of the flange back tester until the chart image comes into focus.
 

Also check the optical axis aligns with the chart center. (Refer to Fig. 4-3-4.)
Note: 

Figure shows example. The cause depends on individual lens.

 

Optical Alignment
Best alignment

Incorrect aligned
e.g. As the focusing knob is turned, the chart may appear blurry as illustrated.
The cause depends on individual lens.

4)  Perform Step (1) through Step (6) and ensure that the AS and CB values are within specifications. 

  If the specification is  CB  only, steps 1 to 3 are not required.

 AS 

(astigmatism)

 

The phenomenon where the flare on the ring chart appears in a cruciform shape with the ring chart in the sharpest focus. 
(Fig. 4-3-5 (a))

(1)  Turn the focusing knob until the flare becomes minimum between two approximately opposite points on the ring chart 

edge (as shown with the arrows in Fig. 4-3-5 (b)), and then read the dial gauge value. <A>

(2)  Turn the focusing knob until the flare becomes minimum between two points with the phase of the flare rotated by 90 

degrees from the above condition (as shown with two arrows in Fig. 4-3-5 (c)), and then read the dial gauge value. <B>

(3)  Calculate the AS value (absolute difference between <A> and <B>) and ensure that it is within specifications.
 

AS value = <A> - <B>

 CB 

(Center 

Blur)

 

The phenomenon where the flare on the ring chart trails in one direction with the ring chart in the sharpest focus. 
(Fig. 4-3-5 (d))

(4)  Turn the focusing knob until the ring chart edge in the direction of the maximum flare is in the sharpest focus (as 

shown with the arrow in Fig. 4-3-5 (e)), and then read the dial gauge value. <C>

(5)  Turn the focusing knob until the ring chart edge, opposite 180 degrees from the above condition (as shown with the ar-

row in Fig. 4-3-5 (f)) is in focus, and then read the dial gauge value. <D>

(6)  Calculate the CB value (absolute difference between <C> and <D>) and ensure that it is within specifications.
 

CB value = <C> - <D>

 

(1)

(1)

(2)

(2)

(5)

(4)

AS

E

D

F

H

G

I

CB

CB (Deflection from center)

0.08

AS (AS on the axis)

0.05

5)  If the specifications of CB and AS are not satisfied, perform the  4-3-2. Optical Axis Adjustment .
6)  When their values meet the specification, perform  4-4-1. Projective Resolving Power Check .

1.  Check the flange back value at WIDE (28 mm) or TELE (75 mm), and check CB.
2.  Remove the rear light shield barrel.
3.  Move the zoom to TELE direction, loosen the sems screws of the instruction a little. 

  Remove the adhesive bond bonded to the 4th group frame B assy.

When the adhesive bond cannot be removed, adjust it after replacing the 4th group B assy.

SAL2875 (2.8/28-75 SAM) (28-75mm F2.8 SAM)

4-6

4.  Move the 4th group frame B assy in the direction where CB is generated, tighten the sems screws loosened by step 3.

Rear Light Shield Barrel

Sems Screws

Sems Screw

4th Group Frame B Assy

4th Group 
Frame B Assy

*Apply it to three directions 
  in the same way

Apply the adhesive bond (B-110)
(sides of the Sems Screw)

Apply the adhesive bond (B-110)
(between the Sems Screw)

5.  Install the rear light shield barrel, perform  4-3-1. Optical Axis Check , and repeat the steps 1 to 4 until the specification is sat-

isfied.

6.  After adjustment, apply the adhesive bond (B-110) as shown in Fig.4-3-6.

Setting of Lens Test Projector.

Lens Test Projector and Variable Transformer (Output voltage: AC 100 V)
Note: 

Connect the variable transformer (Output voltage: AC 100 V) to the lens test projector.

A-mount Attachment
Screen (Art paper)
Tape Measure
Plane Mirror (For SLRs)

1. Preparations
1)  Perform the following steps (1) to (3), and incorporate the internal lenses of the lens test projector according to the checking 

focal length.
(1)  Open the lid of the lens test projector.
(2)  Pull up and turn the fixed levers on the right and left sides of the lens test projector.
(3)  Remove or insert the lens.

Be sure to have the right position and direction of the lens.  

 

Lens test projector

Incorporate of the lenses
according to the checking focal-length (f).

Lens

Fixed lever

Fixed lever

Lid

f=18 to 35 mm

f=35 to 100 mm

f=100 to 200 mm

f=200 to 300 mm

Heat-absorbing filter 

Chart

Chart

Chart

Chart

Filament

Filament

Filament

Filament

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•
•
•
•

SAL2875 (2.8/28-75 SAM) (28-75mm F2.8 SAM)

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2)  Attach the checking lens to the lens test projector, and set the equipment as shown in Fig. 4-4-2.
3)  Turn the fan switch of the lens test projector to ON, then turn the lamp switch to ON.  

 

Distance

Lens test projector

Chart

Fan switch

Lamp switch

Plane mirror

Screen

A-mount attachment

Checking lens

F

L

4)  Turn the focus ring of the checking lens until the chart image projected on the screen is the sharpest at the center (y  = 0).
5)  Set the plane mirror to the center of the projected image (y  = 0), and adjust the projector position so that the mirror reflects 

the light to the center of the lens.

2.  Projective Resolving Power Checking Method
1)  Turn the focus ring of the checking lens until the chart image projected on the screen is the sharpest at the center (y  = 0).
2)  Read the number of the smallest pitched lines at the center (y  = 0).

 

The number represents for lines per mm.

Sagittal (S)

Meridional (M)

3)  Rotate the mount rotational plate of the lens projector while observing y  = 9, y  = 12, y  = 15 or y  = 18 and stop it at the loca-

tion where the projective resolving power is worst (low).

 

Read the number of the smallest pitched lines (both sagittal and meridional: 3 lines) at the peripheral point.
Note: 

When reading the number of the smallest pitched lines, be careful of the spurious resolution.

Spurious resolution is the reversed image of 2 or 4 lines which appears on screen when focus is beyond maximum revolving power 
as shown in Fig. 4-4-4.

 

 

Do not confuse spurious resolution for the smallest pitched lines.

 

Correct resolution

Spurious resolution

4)  Change the focal length and projected length of the checking lens. (In case of the zoom lens), project the S image and the M 

image at each focal point/projected length and confirm that the number of resolution satisfies the specification of the Table 4-
4-1.

Focal length 

f (mm)

Distance (m)

Number of the smallest pitched (lines/mm)

Center (y' = 0)

Peripheral (y' = 15)

Peripheral (y' = 18)

S

M

S

M

28

1.1

100 lines or 

greater

25 lines or 

greater

25 lines or 

greater

25 lines or 

greater

25 lines or 

greater

50

2.0

75

3.0

5)  Check the projective resolving power. If the projective resolving power does not meet the specification, perform  4-4-2. Pro-

jective Resolving Power Adjustment

  Check the projective resolving power. If the specification is not satisfied, perform the projective resolving power adjustment.

1.  Check the projective resolving power in the state of WIDE end (28 mm), and check the partial blur (front-focus, back-focus).
2.  Remove the rear light shield barrel.
3.  Move the zoom to TELE direction, loosen the sems screws of the instruction a little. 

  Remove the adhesive bond bonded to the 4th group assy.

When the adhesive bond cannot be removed, adjust it after replacing the 4th group assy.

4.  Move the 4th group assy from back-focus tendency to front-focus tendency, tighten the sems screws loosened by step 3.

Rear Light Shield Barrel

Sems Screws

Sems Screw

4th Group Assy

4th Group Assy

*Apply it to three directions 
  in the same way

Apply the adhesive bond (B-110)
(sides of the Sems Screw)

Apply the adhesive bond (B-110)
(between the Sems Screw)

5.  Install the rear light shield barrel, Perform the  4-4-1. Projective Resolving Power Check  again, and repeat the steps 1 to 4 

until the specification is satisfied.

6.  After adjustment, apply the adhesive bond (B-110) as shown in Fig.4-4-5.