Frequently Asked Questions
The following are the three most frequently asked questions:
1. What is the size of a CCD imager?
Expect 1/3", 1/2", rarely 2/3".
If the CCD imager is 1/3" you need a 1/3" lens
(1/2" and 2/3" will work).
If the CCD imager is 1/2" you need a 1/2" lens
(2/3" will work).
If the CCD imager is 2/3" you need a 2/3" lens.
2. Should I use
a manual iris or an auto iris lens?
You can save money by using a manual iris lens when the
scene illumination never changes, for example, an illuminated
store, office or inside a warehouse.
An auto iris lens is always a better choice, especially when
there is outside light or direct light where the camera is
pointing.
3. What focal
length lens do I need?
The smaller focal length number, the wider the field of
view. If you have a camera in an office or warehouse and you want
to see as much as you can, you should use a 2.9mm or 4mm lens
(wide, somewhat distant view). If you want to observe a limited
area, like an entrance, or if you want to see detail close up, use
an 8mm or 12mm lens (narrower view and objects are closer).
The rule: use varifocal lenses for flexibility and the best
field of view.
|
Lens Chart (Field of View) |
|
Lens Size |
Viewing Angle |
5' Away |
10' Away |
15' Away |
25' Away |
50' Away |
100' Away |
|
(mm) |
H |
V |
H |
V |
H |
V |
H |
V |
H |
V |
H |
V |
H |
V |
|
2.9 |
90º |
67º |
10.0 |
6.6 |
20.0 |
13.2 |
30.0 |
19.9 |
50.0 |
33.1 |
100.0 |
66.2 |
200.0 |
132.0 |
|
3.6 |
74º |
55º |
7.5 |
5.2 |
15.1 |
10.4 |
22.6 |
15.6 |
37.7 |
26.1 |
75.4 |
52.1 |
151.0 |
104.0 |
|
6 |
42º |
32º |
3.8 |
2.9 |
7.7 |
5.7 |
11.5 |
8.6 |
19.2 |
14.4 |
38.4 |
28.7 |
77.0 |
57.0 |
|
8 |
32º |
24º |
2.9 |
2.1 |
5.7 |
4.3 |
8.6 |
6.4 |
14.4 |
10.7 |
28.7 |
21.3 |
57.0 |
43.0 |
|
12 |
22º |
17º |
1.9 |
1.5 |
3.9 |
3.0 |
5.8 |
4.5 |
9.7 |
7.5 |
19.4 |
14.9 |
39.0 |
30.0 |
|
16 |
15º |
11º |
1.3 |
1.0 |
2.6 |
1.9 |
3.9 |
2.9 |
6.6 |
4.8 |
13.2 |
19.6 |
26.0 |
19.0 |
Technical
Information:
Auto Iris Lens: a lens in which the iris aperture
automatically opens or closes to maintain proper light levels on
the faceplate of the camera pickup device.
Video Type Auto
Iris Lens: an auto-iris lens with internal circuit which
receives voltage and a video signal from the camera to adjust the
iris.
DC Type Auto Iris
Lens: an auto-iris lens without an internal circuit to
control the iris. All iris control voltages come from a circuit
located within the camera.
Manual Iris
Lens: a
lens with a manual adjustment to set the iris opening (f-stop) in
a fixed position. Generally used for fixed lighting applications.
Angle of View: the
angular range that can be focused within the image size. Small
focal lengths give a wide angle of view, and large focal lengths give
a narrow field of view.
F-Stop: a
term used to indicate the speed of a lens. The smaller the
f-number, the greater is the amount of light passing through the
lens.
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