be growing out of his or her collar or supporting his or her  head. The background should be subordinate to the main subject in both tone and interest. It should also make the subject stand out and present it to best advantage. Unsharpness and blur are effective ways for separating the subject from the background. Unsharpness can be accomplished by using a relatively large f/stop to render the background out of focus. In the case of subjects in motion,  the  subject  can  be  pictured  sharply  and  the background blurred by panning the subject (fig. 5-20). Occasionally, you may want to reverse these effects and record   the   subject   unsharp   or   blurred   and   the background sharp. This is done to create the impression of the subject being closer to the viewer or to express motion by holding the camera still as you use a shutter speed that is too slow to “stop” the motion. PERSPECTIVE Perspective  refers  to  the  relationship  of  imaged objects  in  a  photograph.  This  includes  their  relative positions and sizes and the space between them. In other words, perspective in the composition of a photograph is the way real three-dimensional objects are pictured in a photograph that has a two-dimensional plane. In photography, perspective is another illusion you use to produce  photographs  of  quality  composition. When you are making pictures, the camera always creates perspective. Because a camera automatically produces perspective, many novice photographers believe there is no need to know much about it. This attitude  is  far  from  correct.  When  you  know  the principles of perspective and skillfully apply them, the photographs you produce show a good rendition of the subject's form and shape, and the viewer is given the sensation  of  volume,  space,  depth,  and  distance. Additionally,   the   photographer   can   manipulate perspective  to  change  the  illusion  of  space  and  distance by either expanding or compressing these factors, therefore providing a sense of scale within the picture. Linear   Perspective The human eye judges distance by the way elements within a scene diminish in size, and the angle at which lines  and  planes  converge.  This  is  called  linear perspective. The distance between camera and subject and the lens  focal  length  are  critical  factors  affecting  linear perspective. This perspective changes as the camera position or viewpoint changes. From a given position, changing only the lens focal length, and not the camera position, does not change the actual viewpoint, but may change  the  apparent  viewpoint. The   use   of   different   focal-length   lenses   in combination  with  different  lens-to-subject  distances helps you alter linear perspective in your pictures. When the  focal  length  of  the  lens  is  changed  but  the lens-to-subject distance remains unchanged, there is a change in the image size of the objects, but no change in   perspective.   On   the   other   hand,   when   the lens-to-subject distance and lens focal length are both changed,  the  relationship  between  objects  is  altered  and perspective  is  changed.  By  using  the  right  combination of camera-to-subject distance and lens focal length, a photographer can create a picture that looks deep or shallow. This feeling of depth or shallowness is only an illusion,  but  it  is  an  important  compositional  factor. Using  a  short-focal-length  lens  from  a  close camera-to-subject distance, or viewpoint, produces a picture with greater depth (not to be confused with depth of field) than would be produced with a standard lens. Conversely,  using  a  long-focal-length  lens  from  a  more distant viewpoint produces a picture with less apparent depth. Rectilinear   Perspective Most  lenses  produce  rectilinear  perspective  that  are typical of what the human eye sees. This is to say that lines that are straight in the subject are reproduced straight in the picture. Most pictures are made with rectilinear  lenses. Fisheye lenses and the lenses used on panoramic cameras produce a false perspective. A panoramic lens produces  panoramic  or  cylindrical  perspective.  In  other words,  all  straight  horizontal  lines  at  the  lens  axis  level are recorded as straight lines, and all other straight horizontal lines either above or below the lens axis level are  reproduced  as  curved  lines.  The  other  false perspective is produced by a fisheye lens in which all straight lines in the subject are imaged as curved lines toward the edges of the picture. Vanishing  Point  Perspective In vision, lines that are parallel to each other give the  sensation  of  meeting  at  vanishing  points.  When parallel   lines,   either   horizontal   or   vertical,   are perpendicular to the lens axis, the vanishing points are assumed to be at infinity. Other lines, those which are parallel to the lens axis, and all other parallel lines at all other angles to the lens axis meet at definable vanishing 5-23