The question of whether a video image is usable or not depends on the purpose of the system. This may range from the ability to simply perceive a change in the frame right up to the reliable identification of a person that would stand up in a court of law. As specified in the DIN EN 62676-4 standard, there are currently six different levels of quality for video surveillance. "Inspect" is the level with the highest demands on image quality, whereas "Monitor" is the one with the lowest.
|
DIN EN EN 62676-4 |
Monitor |
Detect |
Observe |
Recognize |
Identifiy |
Inspect |
|---|---|---|---|---|---|---|
|
Millimeters per pixel (scene width) |
80 |
40 |
16 |
8 |
4 |
1 |
|
Pixels per 16 cm (face) |
2 |
4 |
10 |
20 |
40 |
160 |
These parameters can be used to determine the maximum distance between camera and surveillance area (location), the minimum resolution to match the camera location, and the most suitable camera lens for optimal coverage of the surveillance area.
The table shows the maximum distances and image widths (camera ↔ surveillance area) for the different quality levels and resolutions. Please select a lens, an image sensor and another unit if necessary.
|
Quality Levels
|
||||||
|---|---|---|---|---|---|---|
| Image size |
Distance
Image width
|
Distance
Image width
|
Distance
Image width
|
Distance
Image width
|
Distance
Image width
|
Distance
Image width
|
|
CIF
320 x 240
|
14,23 m
29,48 m
|
7,12 m
14,74 m
|
2,85 m
5,90 m
|
1,42 m
2,95 m
|
0,71 m
1,47 m
|
0,18 m
0,37 m
|
|
VGA
640 x 480
|
28,47 m
58,95 m
|
14,23 m
29,48 m
|
5,69 m
11,79 m
|
2,85 m
5,90 m
|
1,42 m
2,95 m
|
0,36 m
0,74 m
|
|
HD
960 x 720
|
42,70 m
88,43 m
|
21,35 m
44,21 m
|
8,54 m
17,69 m
|
4,27 m
8,84 m
|
2,13 m
4,42 m
|
0,53 m
1,11 m
|
|
MEGA
1280 x 960
|
56,93 m
117,91 m
|
28,47 m
58,95 m
|
11,39 m
23,58 m
|
5,69 m
11,79 m
|
2,85 m
5,90 m
|
0,71 m
1,47 m
|
|
QXGA
1920 x 1536
|
91,09 m
188,65 m
|
45,54 m
94,32 m
|
18,22 m
37,73 m
|
9,11 m
18,86 m
|
4,55 m
9,43 m
|
1,14 m
2,36 m
|
|
5MP
2592 x 1944
|
115,28 m
238,76 m
|
57,64 m
119,38 m
|
23,06 m
47,75 m
|
11,53 m
23,88 m
|
5,76 m
11,94 m
|
1,44 m
2,98 m
|
Hemispheric cameras with 180° horizontal image angle (lens B016/L10-L12)
Thanks to its hemispherical 180° lens, a single camera can monitor an entire room right into each of the four corners – and is primarily suited to providing an excellent overview, and less suitable for more exact details. People, for example, may be identified very well at distances of up to 1.5 m, and with sufficient detail at up to 3 m. Objects can be recognized even at distances of 5 m and more from the camera. If you would only like to know if persons enter a room, or to monitor specific objects, rooms of up to 100 m2 floor area can be monitored using a single camera.
The image quality (precision) diminishes as the distance of an object to the camera focus point increases:
- 1 = very good,
- 2 = good
- 3 = satisfactory