4-20
SAL24105 (3.5-4.5/24-105) (24-105mm F3.5-4.5)
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).
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 or 18) 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)
Change the focal-length (zoom) and distance of the checking lens, and check that the all readings (y’= 0, y’= 12 (f=24, meridional
(M) only) saggital (S) and meridional (M) at y’= 15 or 18) at each focal-length (zoom) and distance is within the specification of the
Table 4-3-2.
Specification
Focal-length distance (m)
Number of the smallest pitched lines
f (mm)
Center (y’=0)
y’= 12 (Lines per mm)
y’= 15 (Lines per mm)
y’= 18 (Lines per mm)
(Lines per mm)
S
M
S
M
S
M
24
1.1
125 or greater
—
25 or greater 40 or greater 32 or greater 25 or greater 25 or greater
50
2.0
125 or greater
—
—
40 or greater 32 or greater 40 or greater 25 or greater
105
4.0
125 or greater
—
—
40 or greater 25 or greater 40 or greater 25 or greater
Table 4-3-2
The number represents for lines per mm.
Saggital (S)
Meridional (M)
Correct resolution
Spurious resolution
