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Верзија на датум 16. септембар 2020. у 03:58

Za mnoge kamere, ubina polja (engl. depth of field, DOF) rastojanje je između najbližeg i najdaljeg objekta koji su prihvatljivo oštrom fokusu u slici. Dubinska oštrina se može izračunati na osnovu žižne daljine, udaljenosti od objekta, prihvatljivog kruga zabune i otvora blende. Određena dubina polja može se odabrati u tehničke ili umetničke svrhe. Ograničenja dubinske oštrine ponekad se mogu prevazići različitim tehnikama/opremom.

Makro fotografija ilustruje efekat dubine polja na nagnutom objektu.

Faktori koji utiču na dubinu polja

 
Effect of aperture on blur and DOF. The points in focus (2) project points onto the image plane (5), but points at different distances (1 and 3) project blurred images, or circles of confusion. Decreasing the aperture size (4) reduces the size of the blur spots for points not in the focused plane, so that the blurring is imperceptible, and all points are within the DOF.

For cameras that can only focus on one object distance at a time, depth of field is the distance between the nearest and the farthest objects that are in acceptably sharp focus.[1] "Acceptably sharp focus" is defined using a property called the circle of confusion.

The depth of field can be determined by focal length, distance to subject, the acceptable circle of confusion size, and aperture.[2] The approximate depth of field can be given by:

 

for a given circle of confusion (c), focal length (f), f-number (N), and distance to subject (u).[3][4]

As distance or the size of the acceptable circle of confusion increases, the depth of field increases; however, increasing the size of the aperture or increasing the focal length reduces the depth of field. Depth of Field changes linearly with F-number and circle of confusion, but changes in proportional to the square of the focal length and the distance to the subject. As a result, photos taken at extremely close range have a proportionally much smaller depth of field.

Sensor size affects DOF in counterintuitive ways. Because the circle of confusion is directly tied to the sensor size, decreasing the size of the sensor while holding focal length and aperture constant will decrease the depth of field (by the crop factor). The resulting image however will have a different field of view. If the focal length is altered to maintain the field of view, the change in focal length will counter the decrease of DOF from the smaller sensor and increase the depth of field (also by the crop factor). [5][6][7][8]

Efekat aperture sočiva

For a given subject framing and camera position, the DOF is controlled by the lens aperture diameter, which is usually specified as the f-number (the ratio of lens focal length to aperture diameter). Reducing the aperture diameter (increasing the f-number) increases the DOF because only the light travelling at shallower angles passes through the aperture. Because the angles are shallow, the light rays are within the acceptable circle of confusion for a greater distance.[9]

Motion pictures make only limited use of this control; to produce a consistent image quality from shot to shot, cinematographers usually choose a single aperture setting for interiors and another for exteriors, and adjust exposure through the use of camera filters or light levels. Aperture settings are adjusted more frequently in still photography, where variations in depth of field are used to produce a variety of special effects.

 
Aperture = f/1.4. DOF=0.8 cm
 
Aperture = f/4.0. DOF=2.2 cm
 
Aperture = f/22. DOF=12.4 cm
Depth of field for different values of aperture using 50 mm objective lens and full-frame DSLR camera. Focus point is on the first blocks column.[10]

Efekat kruga zabune

Precise focus is only possible at an exact distance from the lens;[а] at that distance, a point object will produce a point image. Otherwise, a point object will produce a blur spot shaped like the aperture, typically and approximately a circle. When this circular spot is sufficiently small, it is visually indistinguishable from a point, and appears to be in focus. The diameter of the largest circle that is indistinguishable from a point is known as the acceptable circle of confusion, or informally, simply as the circle of confusion. Points that produce a blur spot smaller than this acceptable circle of confusion are considered acceptably sharp.

The acceptable circle of confusion depends on how the final image will be used. It is generally accepted to be 0.25 mm for an image viewed from 25 cm away.[11]

For 35 mm motion pictures, the image area on the film is roughly 22 mm by 16 mm. The limit of tolerable error was traditionally set at 0.05 mm (0.002 in) diameter, while for 16 mm film, where the size is about half as large, the tolerance is stricter, 0.025 mm (0.001 in).[12] More modern practice for 35 mm productions set the circle of confusion limit at 0.025 mm (0.001 in).[13]

Napomene

  1. ^ strictly, at an exact distance from a plane

Reference

  1. ^ Salvaggio & Stroebel 2009, стр. 110-.
  2. ^ Barbara London; Jim Stone; John Upton (2005). Photography (8th изд.). Pearson. стр. 58. ISBN 978-0-13-448202-6. 
  3. ^ Elizabeth Allen; Sophie Triantaphillidou (2011). The Manual of Photography. Taylor & Francis. стр. 111—. ISBN 978-0-240-52037-7. 
  4. ^ „Depth of field”. graphics.stanford.edu. 
  5. ^ Nasse, H.H. (март 2010). „Depth of Field and Bokeh (Zeiss Whitepaper)” (PDF). lenspire.zeiss.com. 
  6. ^ „Digital Camera Sensor Sizes: How it Influences Your Photography”. www.cambridgeincolour.com. 
  7. ^ „Sensor Size, Perspective and Depth of Field”. Photography Life. 
  8. ^ Vinson, Jason (22. 1. 2016). „The Smaller the Sensor Size, the Shallower Your Depth of Field”. Fstoppers (на језику: енглески). 
  9. ^ Why Does a Small Aperture Increase Depth of Field?
  10. ^ „photoskop: Interactive Photography Lessons”. 25. 4. 2015. 
  11. ^ Savazzi 2011, стр. 109.
  12. ^ Film and Its Techniques. University of California Press. 1966. стр. 56. Приступљено 24. 2. 2016. 
  13. ^ Thomas Ohanian and Natalie Phillips (2013). Digital Filmmaking: The Changing Art and Craft of Making Motion Pictures. CRC Press. стр. 96. ISBN 9781136053542. Приступљено 24. 2. 2016. 

Literatura

  • Salvaggio, Nanette; Stroebel, Leslie (2009). Basic Photographic Materials and Processes. Taylor & Francis. стр. 110—. ISBN 978-0-240-80984-7. 
  • Adams, Ansel (1980). The Camera  (на језику: енглески). New York Graphic Society. ISBN 9780821210925. „Adams, Ansel. 1980. The Camera.” 
  • Couzin, Dennis. 1982. Depths of Field. SMPTE Journal, November 1982, 1096–1098. Available in PDF at https://sites.google.com/site/cinetechinfo/atts/dof_82.pdf.
  • Gibson, H. Lou. 1975. Close-Up Photography and Photomacrography. 2nd combined ed. Kodak Publication No. N-16. Rochester, NY: Eastman Kodak Company, Vol II: Photomacrography. ISBN 0-87985-160-0
  • Hansma, Paul K. 1996. View Camera Focusing in Practice. Photo Techniques, March/April 1996, 54–57. Available as GIF images on the Large Format page.
  • Hopkins, H.H. 1955. The frequency response of a defocused optical system. Proceedings of the Royal Society A, 231:91–103.
  • Lefkowitz, Lester. 1979 The Manual of Close-Up Photography. Garden City, NY: Amphoto. ISBN 0-8174-2456-3
  • Merklinger, Harold M. 1992. The INs and OUTs of FOCUS: An Alternative Way to Estimate Depth-of-Field and Sharpness in the Photographic Image. v. 1.0.3. Bedford, Nova Scotia: Seaboard Printing Limited. ISBN 0-9695025-0-8. Version 1.03e available in PDF at http://www.trenholm.org/hmmerk/.
  • Merklinger, Harold M. 1993. Focusing the View Camera: A Scientific Way to Focus the View Camera and Estimate Depth of Field. v. 1.0. Bedford, Nova Scotia: Seaboard Printing Limited. ISBN 0-9695025-2-4. Version 1.6.1 available in PDF at http://www.trenholm.org/hmmerk/.
  • Peterson, Stephen. 1996. Image Sharpness and Focusing the View Camera. Photo Techniques, March/April 1996, 51–53. Available as GIF images on the Large Format page.
  • Ray, Sidney F. 1994. Photographic Lenses and Optics. Oxford: Focal Press. ISBN 0-240-51387-8
  • Ray, Sidney F. 2000. The geometry of image formation. In The Manual of Photography: Photographic and Digital Imaging, 9th ed. Ed. Ralph E. Jacobson, Sidney F. Ray, Geoffrey G. Atteridge, and Norman R. Axford. Oxford: Focal Press. ISBN 0-240-51574-9
  • Ray, Sidney F. 2002. Applied Photographic Optics. 3rd ed. Oxford: Focal Press. ISBN 0-240-51540-4
  • Shipman, Carl. 1977. SLR Photographers Handbook. Tucson: H.P. Books. ISBN 0-912656-59-X
  • Stokseth, Per A. 1969. Properties of a Defocused Optical System. Journal of the Optical Society of America 59:10, Oct. 1969, 1314–1321.
  • Stroebel, Leslie. 1976. View Camera Technique. 3rd ed. London: Focal Press. ISBN 0-240-50901-3
  • Tillmanns, Urs. 1997. Creative Large Format: Basics and Applications. 2nd ed. Feuerthalen, Switzerland: Sinar AG. ISBN 3-7231-0030-9
  • von Rohr, Moritz. 1906. Die optischen Instrumente. Leipzig: B. G. Teubner
  • Williams, Charles S., and Becklund, Orville. 1989. Introduction to the Optical Transfer Function. New York: Wiley. Reprinted 2002, Bellingham, WA: SPIE Press, 293–300. ISBN 0-8194-4336-0
  • Williams, John B. 1990. Image Clarity: High-Resolution Photography. Boston: Focal Press. ISBN 0-240-80033-8
  • Andrew Kay, Jonathan Mather, and Harry Walton, "Extended depth of field by colored apodization", Optics Letters, Vol. 36, Issue 23, pp. 4614–4616 (2011).
  • Savazzi, Enrico (2011). Digital Photography for Science (Hardcover). Lulu.com. ISBN 978-0-557-91133-2. Шаблон:Self-published inline
  • Hummel, Rob (editor). 2001. American Cinematographer Manual. 8th ed. Hollywood: ASC Press. ISBN 0-935578-15-3
  • Kingslake, Rudolf (1951). Lenses in Photography: The Practical Guide to Optics for Photographers. Garden City, NY: Garden City Press. 
  • Sutton, Thomas; Dawson, George (1867). A Dictionary of Photography. London: Sampson Low, Son & Marston. 
  • Optics in Photography - Google Books. Приступљено 24. 9. 2014. 
  • Abney, W. de W. (1881). A Treatise on Photography (First изд.). London: Longmans, Green, and Co. 

Spoljašnje veze

 
Depth of field na Vikimedijinoj ostavi.
Преузето из „https://sr.wikipedia.org/w/index.php?title=Dubina_polja&oldid=23344182”