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===Tilt=== [[File:Front Standard Tilt.png|frame|Front standard tilt]] The axis of the lens is normally perpendicular to the film (or sensor). Changing the angle between axis and film by tilting the lens standard backwards or forwards is called ''lens tilt,'' or just ''tilt.'' Tilt is especially useful in [[landscape photography]]. By using the [[Scheimpflug principle]], the “plane of sharp focus” can be changed so that any plane can be brought into sharp focus. When the film plane and lens plane are parallel as is the case for most 35 mm cameras, the plane of sharp focus is also parallel to these two planes. If, however, the lens plane is tilted with respect to the film plane, the plane of sharp focus is also tilted according to geometrical and optical properties. The three planes intersect in a line below the camera for downward lens tilt. The tilted plane of sharp focus is useful, in that this plane can be made to coincide with a near and far object. Thus, both near and far objects on the plane are in focus. This effect is often incorrectly thought of as increasing the depth of field. Depth of field depends on the focal length, aperture, and subject distance. As long as the photographer wants sharpness in a plane that is parallel to the film, tilt is of no use. However, tilt has a strong effect on the depth of field by drastically altering its shape, making it asymmetrical. Without tilt, the limits of near and far acceptable focus are parallel to the plane of sharp focus as well as parallel to the film. With forward tilt, the plane of sharp focus tilts even more and the near and far limits of acceptable focus form a wedge shape (viewed from the side). Thus, the lens still sees a cone shaped portion of whatever is in front of it while the wedge of acceptable focus is now more closely aligned with this cone. Therefore, depending on the shape of the subject, a wider aperture can be used, lessening concerns about camera stability due to slow shutter speed and diffraction due to too-small aperture. Tilting achieves the desired depth of field using the aperture at which the lens performs best. Too small an aperture risks losses to diffraction and camera/subject motion what is gained from depth of field. Only testing a given scene, or experience, shows whether tilting is better than leaving the standards neutral and relying on the aperture alone to achieve the desired depth of field. If the scene is sharp enough at f/32 with 2 degrees of tilt but would need f/64 with zero tilt, then tilt is the solution. If another scene would need f/45 with or without tilt, then nothing is gained. See Merklinger<ref> Merklinger, H. M. (1996). ''Focusing the View Camera'', p. 67. Bedford, Nova Scotia: Seaboard Printing Limited. {{ISBN|0-9695025-2-4}}. [http://www.trenholm.org/hmmerk/download.html Available for download] (PDF). Page number refers to the electronic edition of 29 December 2006. </ref> and Luong<ref> Luong, Q. T. (2000). [http://www.largeformatphotography.info/how-to-focus.html How to Focus the View Camera]. On the Large Format Page. Retrieved 9 July 2008. </ref> for extensive discussions on determining the optimal tilt (if any) in challenging situations. With a forward tilt, the shape of the portion of a scene in acceptable focus is a wedge. Thus, the scene most likely to benefit from tilting is short in the front and expands to a greater height or thickness toward the horizon. A scene consisting of tall trees in the near, middle and far distance may not lend itself to tilting unless the photographer is willing to sacrifice either the top of the near trees and/or the bottom of the far trees. Assuming lens axis front tilt, here are the trade offs in choosing between a small degree of tilt (say less than 3) and a larger tilt: A small tilt causes a wider or fatter wedge but one that is far off axis from the cone of light seen by the lens. Conversely, a large tilt (say 10 degrees) makes the wedge more aligned with the lens view, but with a narrower wedge. Thus, a modest tilt is often, or even usually, the best starting point. Small and medium format cameras have fixed bodies that do not allow for misalignment of the film and lens planes, intentionally or not. [[Tilt-and-shift lens|Tilt/shift]] (“TS”) or [[perspective control lens|perspective control]] (“PC”) lenses that provide limited movements for these cameras can be purchased from a number of lens makers. High-quality TS or PC lenses are expensive. The price of a new Canon TS-E or Nikon PC-E lens is comparable to that of a good used large-format camera, which offers a much greater range of adjustment. {{Clear}}
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