2. 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).
3)
Turn the mount rotation ring of lens test projector until the projected image at a certain peripheral point (y'= 9 or 12) 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 as shown in Fig.4-4-4.
Do not confuse spurious resolution for the smallest pitched lines.
Correct resolution
4)
Change the focal-length (zoom) and distance of the checking lens, and check that the all readings (y'= 0, saggital (S) and meridional
(M) at y'= 9 or 12) at each focal-length (zoom) and distance is within the specification of the Table 4-4-2.
Specification
Focal-length distance (m)
f (mm)
16
50
105
SAL16105 (DT 3.5-5.6/16-105) (DT 16-105mm F3.5-5.6)
Fig.4-4-3
Spurious resolution
Fig.4-4-4
Center (y'=0)
(Lines per mm)
1.07
125 or greater
40 or greater
3.1
125 or greater
40 or greater
4
125 or greater
40 or greater
Table 4-4-2
The number represents for lines per mm.
Meridional (M)
Number of the smallest pitched lines
y'= 9 (Lines per mm)
S
M
32 or greater
32 or greater
32 or greater
4-23
Saggital (S)
y'= 12 (Lines per mm)
S
M
32 or greater
20 or greater
32 or greater
25 or greater
32 or greater
25 or greater