Key features of a camera lens:
It is essential to choose the right lens depending on the type of application; a wide angle lens is helpful for example in a small room, because the lack of decline will be offset by a very wide angle of vision; If by cons, it is necessary to monitor a detail or a remote location, use a telephoto lens is recommended. Choosing a bad lens can compromise the entire system.
Focal length and field of vision:
The lens focal length is measured in millimeters and corresponds directly to the angle of view will be achieved. The short focal lengths give great viewing angles and focal lengths, produced by telephoto, give narrow viewing angles.
The above table shows the values for a distance of 10m and a camera with VGA resolution of 640 × 480; for a resolution HD 1280 × 800, the values of size 1/4 “approaches the 1/3”.
The opening (F):
The objective generally two types of opening related measures: the maximum aperture (minimum F value) when the lens is fully open, and the minimum aperture (maximum numerical value, F ) just before the lens is completely closed. The opening has some influence on the final image.
A large opening means that the lens can pass more light in the dark and the camera thus produces a better image at night.
A small opening may be necessary in case of light and intense reflection. This prevents the camera to produce too many white and maintains a constant video level.
Fixed infrared (IR)
objectives with infrared Correction are specifically designed for day / night cameras with IR filter switching.
The wavelength of infrared light (night) is different from that visible by the human eye (day), which generates a different focal point, so a focus shift (depth of field).
The use of IR corrected lenses preserves an update identical point of day or night and get a high quality image. A goal treaty allows IR light to converge at the same point on the ENTERTAINMENTDNS, occurring in every case a clear image. an untreated lens IR infrared rays do not focus on the same plane and create a ghost reflection.
Conclusion and tips for choosing the camera:
- If it is necessary to observe the details, it is best to choose a high resolution of 1 megapixel or higher camera.
- Opt instead for the more efficient H.264 compression format.
- Choosing a more sensitive camera improves the image in low light conditions. The sensitivity of a camera is indicated by the minimum amount of light so that the camera generates a usable image.
For example, color 1.0 lux at F1.2, B & W 0.15 lux at F1.2.
- Cameras sited outdoors, take into account IP protection.