Light on Photography

  

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    Classification of lenses    
    Range of lenses      
           
    Normal      
    Wideangle      
    Telephoto      
           
    Speciality lenses      
    Fisheye lens      
    Macro lens      
    Tilt and shift lens      
           
           
           
           

 

    Types of Lenses      
    Since most cameras can be used with interchangeable lenses, a photographer can choose which lens to buy or use. The most important way lenses differ is in their focal length. Focal length is the distance between the lens ( technically, from its rear nodal point) and the focal plane when the lens is focused on infinity (a far distance from which light reaches the lens in approximately parallel rays). A lens is often described in terms of its focal length ( a 50mm lens) or its relative focal length (short, normal, or long).    
    Focal length controls magnification ( The size of the image formed by the lens) and angle of view ( the amount of the scene shown on a given size of film). The effect of focal length on magnification is diagrammed. A lens of short focal length bends light sharply. The rays of light focus close behind the lens and form a small image of the object.    
   

   
    The longer the focal length, the less the lens bends the light rays, the farther behind the lens the image is focused, and more the image is magnified.    
   

   
    The size of the image increases in proportion to the focal length; if the subject remains at the same distance from the lens, the image formed by a 25mm lens will be half as big as that from a 50mm lens.    
    A lens of long focal length forms a larger image of an object, so it includes on a given size of film less of the scene in which the object appears. If you make a circle with your thumb and fore-finger and hold it close to your eye, you will see most of the scene in front of you. If you move your hand farther from your eye, the circle will be filled by a smaller part of the scene: you have decreased the angle of view seen through your fingers. In the same way, the longer the focal length, the smaller the angle of view seen by the lens.
 		    
           
    In photography, angle of view describes the angular extent of a given scene that is imaged by a camera. It parallels, and may be used interchangeably with, the more general visual term field of view

It is important to distinguish the angle of view from the angle of coverage, which describes the angle of projection by the lens onto the focal plane. For most cameras, it may be assumed that the image circle produced by the lens is large enough to cover the film or sensor completely.[1] If the angle of view exceeds the angle of coverage, however, then vignetting will be present in the resulting photograph. For an example of this, see below.

    
           
    The  example on the left show the effect of increasing focal length while keeping the same lens to subject distance: a decrease in the angle of view and an increase in magnification. Since the photographer has not changed position, the sizes of objects within the scene remain the same in relation to each other.    
           
           
    Classification of lenses    
    Range of lenses      
           
    Normal      
    Wideangle      
    Telephoto      
           
    Speciality lenses      
    Fisheye lens      
    Macro lens      
    Tilt and shift lens      
           
           
           
           
           

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