Read Sony SAL135F28 Service Manual online
4-26
SAL135F28 (STF 2.8(T4.5)/135) (135mm F2.8 [T4.5] STF)
2. Checking Method
1)
Turn the distance scale tube 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).
Fig.4-3-3
3)
Turn the mount rotation ring of lens test projector until the projected image at a certain peripheral point (y’= 15) on the screen
appears the most unsharp.
Read the number of the smallest pitched lines (both saggital 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.
Do not confuse spurious resolution for the smallest pitched lines.
Fig.4-3-4
4)
Read the number of the smallest pitched lines for both saggital (S) and meridional (M) at the peripheral point (y’= 18) on the screen
in the same way of step 3).
5)
Check that the all readings (y’= 0, saggital (S) and meridional (M) at y’= 15 and y’= 18) is within the specification of the Table 4-3-2.
When the specification is not satisfied, perform the following procedure.
• Replace the 1 group lens block, or the 2 group front frame block or 2 group rear frame block of the 2 group lens block.
Specification
Focal-length distance (m)
Number of the smallest pitched lines
f (mm)
Center (y’=0)
y’= 15
y’= 18
(Lines per mm)
S
M
S
M
135
5.4
125 or greater
50 or greater
50 or greater
50 or greater 50 or greater
Table 4-3-2
6)
After the checking is completed, turn the lamp switch of the lens test projector to OFF and cool the inside of the lens test projector,
then turn the fan switch to OFF.
The number represents for lines per mm.
Saggital (S)
Meridional (M)
Correct resolution
Spurious resolution
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