Canon PowerShot 350 Service Manual - Page 30

Aperture, focus, Format, f/No., Equivalent

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Part 1: General Information If we take the focal length of the lens to be f, the lens aperture to be F, the permissible circle of confusion to be 8 , and the minimum distance between lens and object to be R/2, then the following formula can be applied: f 2 /F8 + F8 +2f = R or f 2 + 2F8f + (F8 ) 2 - RF8 = 0 The value of f can be determined by substituting specific values for F, 8 , and R in this formula. By the way, because of the screen size of the 1/3-in. CCD, the permissible circle of confusion for the PowerShot 350 is set to 0.0136mm. Table 1-4 shows the design limits (permissible circle of confusion: 0.0136mm, minimum distance: 30cm, 50cm, or 100cm) for fixed-focus lenses using 1/3-in. CCDs. Figure 1-13 graphs the ranges. Table 1-4 Fixed Focus Lens Pan Focus Range / Focal Length / Max. Aperture Max. Aperture f (mm) In focus 30cm - ... (35mm Format) 1.0 2.85 20.55 1.4 3.37 24.30 2.0 4.03 29.06 2.8 4.76 34.33 4.0 5.69 41.03 5.6 6.72 48.46 8 8.03 57.91 11 9.40 67.79 16 11.32 81.64 In focus 50cm - oo (35mm Format) 3.68 4.35 5,20 6.15 7.35 8.69 10.38 12.16 14.64 26.54 32.67 37.50 44.35 55.01 62.67 74.86 87.69 105.6 In focus 1m - .. (35mm Format) 5.21 6.16 7.36 8.71 10.40 12.30 14.70 17.22 20.75 37.57 44.42 53.08 62.81 75.00 88.70 106.0 124.2 149.6 f/No. 16. 11. )8. 8 8 ,8 5. ce> sez, c,s Ci 4. I CI, 43 N PowerShot 350 2. 2. I Po werShot 600 1. 1. I 10 (70) 20 (144) Fig. 1-13 1/3" Format 1 -20 30 mm (f) (216) (35mm Equivalent)

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Part
1:
General
Information
If
we
take
the
focal
length
of
the
lens
to
be
f,
the
lens
aperture
to
be
F,
the
permissible
circle
of
confusion
to
be
8
,
and
the
minimum
distance
between
lens
and
object
to
be
R/2,
then
the
following
formula
can
be
applied:
f
2
/F8
+
F8
+2f
=
R
or
f
2
+
2F8f
+
(F8
)
2
-
RF8
=
0
The
value
of
f
can
be
determined
by
substituting
specific
values
for
F,
8
,
and
R
in
this
formula.
By
the
way,
because
of
the
screen
size
of
the
1/3
-in.
CCD,
the
permissible
circle
of
confusion
for
the
PowerShot
350
is
set
to
0.0136mm.
Table
1-4
shows
the
design
limits
(permissible
circle
of
confusion:
0.0136mm,
minimum
distance:
30cm,
50cm,
or
100cm)
for
fixed
-focus
lenses
using
1/3
-in.
CCDs.
Figure
1-13
graphs
the
ranges.
Table
1-4
Fixed
Focus
Lens
Pan
Focus
Range
/
Focal
Length
/
Max.
Aperture
Max.
Aperture
1.0
1.4
2.0
2.8
4.0
5.6
8
11
16
f
(mm)
In
focus
30cm
-
...
2.85
3.37
4.03
4.76
5.69
6.72
8.03
9.40
11.32
(35mm
Format)
20.55
24.30
29.06
34.33
41.03
48.46
57.91
67.79
81.64
In
focus
50cm
-
oo
3.68
4.35
5,20
6.15
7.35
8.69
10.38
12.16
14.64
(35mm
Format)
26.54
32.67
37.50
44.35
55.01
62.67
74.86
87.69
105.6
In
focus
1m
-
..
5.21
6.16
7.36
8.71
10.40
12.30
14.70
17.22
20.75
(35mm
Format)
37.57
44.42
53.08
62.81
75.00
88.70
106.0
124.2
149.6
f/No.
16.
11.
8.
5.
4.
2.
2.
1.
1.
)
8
8
,8
e
c>
CI,
e
sz,
43
cs
,
Ci
N
I
PowerShot
350
Po
werShot
600
I
I
10
20
30
mm
(f)
(70)
(144)
(216)
(35mm
Equivalent)
Fig.
1-13
1/3"
Format
1
-20