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  When I go on holiday, I always take pictures of buildings in the  places I visit. It doesn't matter where I travel to, there's always  some beautiful architecture just waiting to be appreciated and  photographed.
  The problem is, to get a whole building in a shot, you either  have to move further away than you'd like, or point the camera  upwards in an effort to get the top in as well as the bottom.
  When you do the latter, the verticals in the photo converge  upwards and the building appears narrower at the top than at the  bottom.
  One solution to this issue is to use a wide-angle lens, but this  isn't without its own problems: this type of lens will tend to  include more of the foreground, even as it provides a better shot  of the building. The better answer is to use either a view camera  or a tilt-shift lens on a DSLR.
  Back in the very early days of photography (and even today with  specialist cameras), the camera itself was a very simple affair  comprising two standards or planes – one holding the film  plate (and a ground glass viewfinder) and the other holding the  lens. In between the two was a bellows that didn't let in  light.
  The standards were mounted on one or more rails so they could be  moved closer to or further from each other to focus the image, and  to provide other options like perspective and depth of field.
  Figure 1 illustrates the basic setup.
   Figure 1: The basic schematic of a  view camera
Figure 1: The basic schematic of a  view camera
  Notice that the image is seen upside down in the viewfinder.  DSLRs reverse the image so that the view you see through the  viewfinder is the same way up as the real view.
  Rise and fall
  Since the bellows were flexible and the lens and film standards  were separate, these view cameras could provide a whole set of  effects that are hard to produce with modern point-and-shoots or  DSLRs.
  The first of these were shift movements. The lens could be  raised or lowered (known as rise and fall), or moved from side to  side (the traditional shift), all while keeping it in the same  plane.
  Modern tilt-shift lenses on DSLRs provide much of the same  functionality, but they are specialised pieces of equipment and are  generally very expensive compared to normal prime or zoom  lenses.
  The rise movement on a view camera is important for  architectural photography.
  To properly use the rise shift, the image circle of the lens  must be larger than the rectangle covered by the film. The image  circle is the area of the film plane formed by the cone of light  that comes through the lens.
  The majority of the image circle is masked off, leaving just a  rectangle that exposes the sensor of the camera (or the frame of  film). If the camera's lens is shifted, a different part of the  light cone exposes the sensor or film frame.
  If the image circle is small enough, the film frame will not be  fully exposed to the light and you will get the effect known as  vignetting, where the photo fades and darkens towards the edges and  corners.
  Figure 2 shows what happens with rise shift.
   Figure 2: How the rise shift movement  works with a large image circle
Figure 2: How the rise shift movement  works with a large image circle
  In the first image (I've flipped the view so we're not looking  at it upside down), we see the normal state of affairs: the image  circle encompassing the film frame with the top of the building cut  off. The foreground is also prominent.
  The second image shows the effect of the rise shift: the film  frame is in the same place (we're moving the lens up and down, not  the film standard), but the image circle has moved down. A  different part of the view is captured by the film: the one that  contains the top and bottom of the building.
  I'm sure you can imagine the issues posed by vignetting if the  image circle were smaller than the one shown.
  On reflection
  Side-to-side shift movements are used when photographing  reflective surfaces.
  One way to photograph paintings that are behind glass is to deck  yourself out in black and keep the camera behind a black curtain  with only the lens poking through so that only black surfaces are  reflected (just try that in the National Portrait Gallery).
  Another is to photograph the painting from a slight angle,  making sure that the incident light is behind you so that  reflections go away from the camera, and then fix the perspective  in your favourite photo editing program (Photoshop has such a  feature).
  Alternatively, you can use a left/right shift movement to remove  the reflection of the camera using the same technique as for  architectural photography.
  Tilts and swings
  The other main set of possible movements with a view camera are  called tilts and swings, known collectively as tilt.
  In normal use, the axis of the lens is perpendicular to the  plane of the film or sensor. Even shift movements obey this simple  rule.
  The result of this is that the sharp focus of a photo is a plane  parallel to the film. The wider your aperture, the more obvious  this sharp focus plane is.
  In Figure 3, I took a photo of the word 'tilt' in the Oxford  Modern English Dictionary at an angle with the aperture wide open  to illustrate the focus plane.
   Figure 3: A photo showing the narrow  focus plane and shallow depth of field
Figure 3: A photo showing the narrow  focus plane and shallow depth of field
  There are four planes here: the plane of the sensor, the plane  of the lens, the focus plane (which is parallel to the first two),  and the plane of the page in the book (at an extreme angle, almost  perpendicular to the first three planes).
  Notice how the focus tapers off quickly the further or closer  the text is to the camera.
  With a tilt movement, the lens is tilted up or down with respect  to the film plane – they are no longer parallel. The plane of  the lens now intersects the plane of the film – usually below  the camera.
  More importantly, from some simple geometric proofs known as the  Scheimpflug principle, the focus plane – the part of the view  in focus – also tilts (geometrically it intersects the  previous two at the same position).
  In fact, by varying the tilt, you can bring nearer and farther  parts of the view into focus at the same time (the effect on Figure  3 would be to bring all of the text into focus).
  Notice though that this is not the same as increasing the depth  of field by reducing the size of the aperture; this is a totally  different effect, although a photographer can balance the need for  smaller apertures to increase the depth of field by using a tilt  movement.