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

4-8

In this section, the check/adjustment of focus-shift, which arises from the change of the focal length by zooming, is described.

1000mm Collimator
Flange Back Tester
A-mount Attachment
Flange Back Gauge (43.50 mm)

1. Preparations
1) Perform 1. Preparation  of  4-3. OPTICAL AXIS CHECK/ADJUSTMENT .

2.  Focus-shift (Focal Length) Check
1)  Set the zoom to the TELE end (75 mm).
2) Set to 44.56 mm  by rotating the knob of flange back tester.
3)  Focus by rotating the focus ring from the near end side.
4)  Rotate the zoom TELE 

→

 WIDE and WIDE 

→

 TELE and confirm that the value at each focal length satisfies the specifica-

tion.
Note:

  Do not rotate the focus ring.

Focal Length f (mm) 

Flange Back Value f F (mm)

75

44.56 

±

 0.03 (44.53 to 44.59)

60

50

44.56 

±

 0.09 (44.47 to 44.65)

35

28

44.56 

±

 0.05 (44.51 to 44.61)

5)  If the flange back value (f'F) of the checking lens does not satisfy the specification in Table 4-5-1, perform  4-5-2. Focus-shift 

(Focal Length)/Flange Back (f'F) Adjustment .

3.  Flange Back (f'F) Check
1)  Set the zoom to the TELE end (75 mm) or WIDE end (28 mm) and the focus to the over infinity end.
2)  Adjust the focus by rotating the knob of flange back tester and read the flange back value.

Focal Length f (mm) 

Flange Back Value f F (mm)

75

45.56 

±

 0.15 (45.41 to 45.71)

28

44.64 to 44.79

3)  If the flange back value (f'F) of the checking lens does not satisfy the specification in Table 4-5-2, perform  4-5-2. Focus-shift 

(FocalLength)/Flange Back (f'F) adjustment .

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1. Preparations
Perform  4-5-1. Focus-shift (Focal Length)/Flange back (f'F) Check  and confirm that the flange back value (f'F) of lens to be 
checked does not meet the specification in Table 4-5-1.

2. Adjustment Procedure
1)  Set the zoom to the TELE end (75 mm) and the focus to the over infinity end.
2)  Adjust the focus by rotating the knob of flange back tester and read the flange back value. (f't)
3)  Using the value read in step 2), calculate the amount of increase (or decrease) of 1st lens adjustment washer by the formula be-

low.
T1 = (f't - 45.56)/2  T1: Amount of increase (or decrease) of 1st lens adjustment washer
 

f't:  TELE end (75 mm), flange back value at over infinity end

4)  According to the result in step 3), adjust the thickness of 1st lens adjustment washers.

And according to the thickness of 1st adjustment washer, select the screw.

In case that the amount (T1) of increase (or decrease) of 1st lens adjustment washer is negative (-): Decrease the thickness of 
1st lens adjustment washer.
In case that the amount (T1) of increase (or decrease) of 1st lens adjustment washer is positive (+): Increase the thickness of 
1st lens adjustment washer.

Part No.

Thickness (mm)

4-162-834-01

0.5

4-162-834-21

0.2

4-162-834-31

0.1

Part No.

Part Name

Select Standard

4-162-857-01

BT1P1.7x5B3C

Thickness of 1st lens adjustment washers 1.2 mm or more

4-163-678-01

BT1P1.7x4B3C

Thickness of 1st lens adjustment washers less than 1.2 mm

Filter Screw 
Frame Assy

1st Group Assy

1st Washer

1st Lens Adjustment Washer

5)  Set the zoom to the TELE end (75 mm).
6) Set to 44.56mm  by rotating the knob of flange back tester.
7)  Focus by rotating the focus ring from the near side.
8)  Set the zoom to the WIDE end (28 mm).

  Do not rotate the focus ring.

9)  Adjust the focus by rotating the knob of flange back tester and read the flange back value. (f'w)
10) Using the value read in step 9), calculate the amount of increase (or decrease) of back adjustment washer by the formula below.

TB = f'w - 44.56  TB:  Amount of increase (or decrease) of back adjustment washer
 

f'w:  WIDE end (28 mm), flange back value at optical infinity

•

•

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

4-9

11) According to the result in step 10), adjust the thickness of back 

adjustment washers.

In case that the amount (TB) of increase (or decrease) of 
back adjustment washer is negative (-): Decrease the thick-
ness of back adjustment washer.
In case that the amount (TB) of increase (or decrease) of 
back adjustment washer is positive (+): Increase the thick-
ness of back adjustment washer.

Part No.

Thickness (mm)

4-162-875-21

0.05

4-162-875-31

0.1

4-162-875-41

0.2

12) Set the zoom to the TELE end (75 mm).
13) Set to  44.56 mm  by rotating the knob of flange back tester.
14) Focus by rotating the focus ring from the near side.
15) Set the zoom to the MIDDLE range (50 mm).

  Do not rotate the focus ring.

16) Adjust the focus by rotating the knob of flange back tester and 

read the flange back value. (f'm)

17) Using the value read in step 16), calculate the amount of increase (or decrease) of back adjustment washer by the formula be-

low.
T2 = (f'm - 44.56)/5  T2:  Amount of increase (or decrease) of 2nd lens adjustment washer
 

f'm:  MIDDLE range (50 mm), flange back value at optical infinity

18) According to the result in step 17), adjust the thickness of back adjustment washers.

In case that the amount (T2) of increase (or decrease) of back adjustment washer is negative (-): Decrease the thickness of 
2nd lens adjustment washer.
In case that the amount (T2) of increase (or decrease) of back adjustment washer is positive (+): Increase the thickness of 
2nd lens adjustment washer.

Part No.

Thickness (mm)

4-162-793-11

0.2

4-162-793-21

0.1

4-162-793-51

0.02

2nd Group Assy

2nd Lens Ornament Ring

2nd Lens 
Adjustment Washer

19) Perform  4-5-1. Focus-shift (Focal Length) /Flange Back (f'F) Check , repeat the steps 1) to 18) until the specification is satis-

fied.

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•

•

•

Mount Assy

Back Adjustment 
Washer

Mount Assy

Back Adjustment 
Washer

Shoot images with the lens to be tested and the AE master lens under the following conditions (Note 1), and compare the images 
to check the error amount (Note 2).
Note 1:

 

・

Shooting magnification (60, 40, 20 times)

 

・

Chart for checking the depth area of image-formation (tilting chart 2 types)

 

・

Defocus value  0 

±

 10 

μ

m

The higher the magnification, the focusing error amount becomes the bigger. Therefore, it is easy to judge of result.

 

If the error amount is outside of the range, perform  4-8-5. FOCUSING ERROR AMOUNT ADJUSTMENT (Write 

⊿

SB) .

Chart for checking the depth area of image-formation (40, 60 times)
Acquire the  Chart_for_checking_image_formation_40x_60x_(E).zip  from the each HQ.

Chart for checking the depth area of image-formation (20 times)
Acquire the  Chart_for_checking_image_formation_20x_(E).zip  from the each HQ.

Software
Acquire the following either software from the each HQ.

Software

Camera

DSLR-A700 Defocus checker

DSLR-A700

Defocus Checker 2

SLT-A37/A57/A58/A65/A77/A99

 

Camera (One of DSLR-A700, SLT-A37/A57/A58/A65/A77/A99)
HASP key
Personal Computer (supporting Seus-EX)
AE Master Lens
J-6082-597-A: 50 mm/F1.7
Illumination
J-6082-642-A: Fluorescent Lamp (specified color rendering)
J-6082-643-A: Fluorescent Light Stand (high-frequency lighting type)
Memory Card
Tripod

1. Preparation
1)  Insert the memory card to the camera.
2)  Set the camera and chart for checking the depth area of image-formation as shown in Table 4-6-2, Fig. 4-6-1 and Fig. 4-6-2.

Shooting distance is obtained by shooting magnification and focal length as following.

 

[Shooting distance] = [shooting magnification] 

×

 [focal length]

Select the combination according to the Table 4-6-2 Guidelines table.

  If the shooting distance using a 60 times chart cannot be ensured indoors, temporarily use a combination of 40 times chart or 20 

times chart.

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

4-10

3)  Connect the camera and personal computer (when using HASP Key) with USB cable and activate Defocus Checker 2 or 

DSLR-A700 Defocus checker.

 

In case Defocus Checker 2 is used, click [Connect] to set connection mode.
Note:

  If an abnormal phenomenon appears during installation of the teleconverter, install the user s teleconverter and check it.

 

Selection of 
Shooting magni-
fication

AF Assist Chart (Size) 
Refer to Fig. 4-6-1.

Applicable Camera 
(image sensor type)

Applicable Lens

Calculation example 
of shooting distance 
[shooting magnifica-
tion] 

×

 [focal length] 

= [shooting distance]

60 times 
(middle distance)

AF Assist Chart 60 Times 
(200 mm 

×

 100 mm)

APS-C size type 

All

60 times 

×

 50 mm = 

3000 mm

40 times 
(middle distance)

AF Assist Chart 40 Times 
(132 mm 

×

 66 mm)

35 mm full size type

All

40 times 

×

 50 mm = 

2000 mm

20 times 
(short distance)

AF Assist Chart 20 Times 
(66 mm 

×

 33 mm)

both size available

Macro lens
Lens with a focal 
length of more 
than 300 mm

•
•

20 times 

×

 300 mm = 

6000 mm

 

(100 mm)

(66 mm)

(33 mm)

(200 mm)

(132 mm)

(66 mm)

AF Assist Chart
60 Times

AF Assist Chart
40 Times

AF Assist Chart
20 Times

 

Camera Setting

Exposure mode
Focus Mode
Focus Area

Image Size
Super SteadyShot
Drive Mode

: A (Open Aperture)
: MF
: Spot Focus Area
  (Fixed at the center)
: L
: OFF
: Self-timer

Shooting distance

Set the optical axis to the center 
of the AF assist chart.

AF Assist Chart
(60 Times/40 Times)

Chart for checking the depth area of image-formation
(60 Times/40 Times)

2. Shooting procedure
1)  Click the [Start] of Defocus Checker 2 or DSLR-A700 Defocus checker to start the measurements.
2)  Adjust defocus value to obtain  0 

μ

m  in the manual focus mode.

 

The tolerance is  0 

±

 10 

μ

m . (Fig. 4-6-3)

3)  Click the [Stop] of Defocus Checker 2 or DSLR-A700 Defocus checker.
4)  Shoot an image by self-timer.
5)  Perform the steps 1) to 4) by using the AE master lens and the lens to be tested.

Shoot images with the AE master lens and the lens to be tested using the same camera.

Perform entire work within 10 minutes because values become unstable as the camera temperature increases.

 

 

If the work continues for 10 minutes or longer, cool down the camera and then restart the work.

Since focusing error amount increases in shooting images at a middle or long distance, comprehensive focusing error amount 
cannot be determined correctly only by results with short-distance setting. If the shooting distance using a 60 times chart cannot 
be ensured indoors, take either of the following methods.

 

 

 

 

Use 35 mm full size type camera (SLT-A99) and 40 times chart. (When using the 40 times chart, shooting distance can shorten to 
2/3 of 60 times chart.)

 

 

 

 

Check the focusing error amount of short distance using 20 times chart temporarily. After that, shoot the something images out-
doors in the middle distance for using 60 times chart, and then check the focusing amount of middle distance.

 

Defocus Checker 2
(For SLT-A37/A57/A58/A65/A77/A99)

DSLR-A700 Defocus checker
(For DSLR-A700)

In case Good (0

± less than 10 μm), frame 

of waveform area displays in green.

In case Good (0 

± less than 10 μm), frame 

of waveform area and defocus value display 
in green.

3.  The focusing error amount check
1)  Open the images shot with the lens to be tested and the AE master lens by the image display software on the PC. (Display the 

images at the same pixel magnification.)

2)  Check the displacement between the focus position (peak of image-formation) of the lens to be tested and the focus position of 

the AE master lens. (Refer to Fig. 4-6-4 and Fig. 4-6-5.)

3)  Compare the error amount in step 2) with the reference value of Table 4-6-3 and check whether the error amount is within the 

acceptable range. If the error amount is outside of the range, perform  4-8-5. FOCUSING ERROR AMOUNT ADJUSTMENT 
(Write 

⊿

SB) .

Focal length/

28 - (75 mm)

Distance

(mm)

1.5 m (20 times)

0 

±

 18 

3.0 m (40 times)

0 

±

 74 

4.5 m (60 times)

0 

±

 166 

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

4-11

<For reference 1: shooting image by AE master lens> (Fig. 4-6-4)

Assume it standard image in the setting environment.
If the peak of image-formation is to equal distance with AF assist chart position, it is ideal. In actual fact, the image of before 
and behind the peak is displayed. (Because the environment, the individual difference of camera and lens conditions are com-
bined.)
The image of before and behind the peak, assume it reference standard image.
When shooting the image with sharpness setting of the camera to  +  side, it is easy to distinguish the peak of imaging area 
remarkably.

Enlargement of same pixel magnification

Example of image shot with 
a certain AE master lens under 
a certain environment.

Identifying the peak position of 
image-formation:
• Center of sharpest area
• Center of area with less color fogged
    - Front defocus area: Magenta fogged
    - Rear defocus area: Green fogged

Example where peak position accidentally matches 
the AF Assist Chart position

 

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•

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<For reference 2: The example of focusing error amount value check> (Fig. 4-6-5)
Check the displacement between the focus position (peak of image-formation) of the lens to be tested and the focus position 
(peak of image-formation) of the AE master lens.

Example of decision:
The lens to be tested has a tendency of backward defocusing compared to the AE master lens. The error amount is approx. 14 cm.
Compare this error amount with the reference value and check whether the error amount is within the acceptable range.
If the error amount is outside the acceptable range, perform  4-8-5. FOCUSING ERROR AMOUNT ADJUSTMENT (Write 

⊿

SB) .

Example of image shot with lens to be tested (50 mm F1.4)

Example of image shot with AE master lens

Peak area
(existing around 7 to 8 cm
of the rear scale)

Peak area
(existing around 6 to 7 cm
of the front scale)

Error amount = approx. 14 cm