Wide Angle Lens is known in photography as a lens with an angle that is greater than that corresponding to the natural impression of the human eye. Wide Angle Lens in Digital Photography has the opposite properties of the telephoto lens : It is better than a standard lens and have a shorter focal length.
Basics of Wide Angle Lens
With Wide Angle Lens, larger area can be captured. Wide Angle Lens has characteristic large depth of field. Correspond to the natural human field of vision of about 40 to 50 ° normal lenses were manufactured for medium format film cameras. For smaller film formats and in particular smaller sensor sizes in digital cameras, the normal focal length is reduced accordingly. Wide Angle Lens should not to be confused with telephoto lenses of longer focal length or a zoom lens, which allow adjustment of the focal length, but not necessarily have a wide-angle focal length.

So, Wide Angle Lens in Digital Photography needs some extra adjustment during manufacturing because of variable sensor size and resultant Crop Factor.
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More on Wide Angle Lens
Wide Angle Lens has a wide-angle effect, which is established at a diagonal angle between 60 ° and 75 ° and a small image relative to a focal length. Super Wide Angle Lens or Ultra Wide Angle Lens are used in art and nature photography to achieve spectacular effects of distortion typical for these focal lengths.
Wide Angle Lens can be used as an interchangeable lens with proper DSLR body. There are also Wide Angle Lens, actually an attachment that can be mounted over the zoom lens acting as a converter.
Most Wide Angle Lens used in Film Photography usually can not be mounted on a Digital Single Reflex Camera due to the difference in mounting system, crop factor, lack of electronic control resulting in loss of autofocus.
