In photography and cinematography, a wide-angle lens is a lens whose focal length is shorter than the focal length of a normal lens. For a 35 mmcamera with a 24 by 36 mm format, the normal lens is 50 mm. A lens of focal length 35 mm or less is considered wide-angle.
In addition to giving a wider angle of view, the resulting image can also have perspective distortion.
Extreme wide-angle lenses normally do not give a geometric projection, and are called fisheye lenses.
See angle of view for an example of an image taken by a wide-angle lens.
The challenge is to design a lens that collects light from a wide area (i.e., from the entire room) and yields an image that is "perspectively correct," in that it accurately depicts the shapes and relative dimensions of imaged objects.
This "refractive" lens produces a sharp image of the large area at the exact location of the image sensor within the bullet camera.
The v-shaped lens is called a catoptric (reflective) lens and the second lens is known as a dioptric (refractive) lens, so the combined design is called a "catadioptric" lens.
For normal lens (of in reallity) this vanishing point is somewhat farter from the focal plane than for the wide-angle lens — the intersection of the blue line and the axis.
Wideangle means that you can fit a lot of stuff into the image, like on the image to the left.
Wideanglelens help when there is a limited space and you need to jam a big subject into the picture.
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