عمق الحقل

A macro photograph with very shallow depth of field.

Shallow depth of field can yield dramatic results and greatly emphasize the subject.

عمق الميدان أو الحقل Depth of field واختصارها DOF وهي المسافة بين الجسم القريب والخلفية الأبعد والخارجة عن نطاق التركيز في الصورة وكمثال : عندما تصور شخص ويكون واضح المعالم في الصورة ولكن الخلفي أو المنظر الذي خلفة يكون غير واضح وخارج نطاق التركيز. ويمكن التحكم بهذا الشيء بواسطة فتحة العدسة APERTURE فإذا زادت الفتحة قل عمق الميدان والعكس عند تصوير المناظر الطبيعية مثلا.

A 35 mm lens set to f/11. The depth-of-field scale (top) indicates that a subject which is anywhere between 1 and 2 meters in front of the camera will be rendered acceptably sharp. If the aperture were set to f/22 instead, everything from 0.7 meters to infinity would appear to be in focus.

المساحة ضمن عمق الحقل تبدو حادة الملامح، بينما المساحات أمام وخلف عمق الحقل تبدو ضبابية.

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.

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 تعريف

Detail from the lens shown above. The point half-way between the 1 m and 2 m marks represents approximately 1.3 m.

هو عبارة عن مؤشر يبيّن نسبة المساحة التي ستبقى واضحة وضمن التركيز البؤري في المشهد المراد تصويره. والعمق الحقلي الكبير يعني مسافة متزايدة بين خلفية الصورة ذات التركيز البؤري الجيد وأمامية الصورة، مع تركيز بؤري جيد لكل شيء يقع بينهما. أما العمق الحقلي الضيّق فإنه يركز بؤرته على مجال صغير، اعتماداً على بعد العنصر المركزي عن الكاميرا. وعلى سبيل المثال، إذا كان موضوع التصوير هو شخص يقف بمفرده في حديقة، فإن استخدام عمق حقلي ضيق سيؤدي إلى أن معظم الحديقة ستبدو غير واضحة في الصورة، وسيبقى التركيز البؤري مركزاً على الشخص فقط. أما عند استخدام عمق حقلي كبير، فإننا سنحافظ على بقاء معظم الحديقة ضمن التركيز البؤري.

 معرض الصور

• DOF with various apertures
• 

  f/22

• 

  f/8

• 

  f/4

• 

  f/2.8

At f/32, the background competes for the viewer’s attention.

At f/5.6, the flowers are isolated from the background.

At f/2.8, the cat is isolated from the background.

The integrated circuit package, which is in focus in this macro shot, is 2.5 mm higher than the circuit board it is mounted on. In macro photography even small distances can blur an object out of focus. At f/32 every object is within the DOF, whereas the closer one gets to f/5, the fewer the objects that are sharp. The images were taken with a 105 mm f/2.8 macro lens. At f/5 the small dust particles at the bottom right corner set examples for the circle of confusion phenomenon.

Series of images demonstrating a 6 image focus bracket of A Tachinid fly. First two images illustrate typical DOF of a single image at f/10 while the third image is the composite of 6 images.

DOF for symmetrical lens.

Defocus blur for background object at B.

 انظر ايضاً

• Angle of view
• Bokeh
• Circle of confusion
• Numerical aperture
• Deep focus
• Depth-of-field adapter
• Depth of focus
• Frazier lens (very deep DOF)
• Hyperfocal distance
• Perspective distortion
• Shallow focus
• Tilted plane focus (camera movements used to achieve selective focus)
• Miniature faking

 المصادر

• موقع أصدقاء الضوء
• Adams, Ansel. 1980. The Camera. The New Ansel Adams Photography Series/Book 1. Boston: New York Graphic Society. ISBN 0-8212-1092-0
• Canon Inc. 2000. Canon EOS-1v/EOS-1v HS Instructions. Tokyo: Canon Inc.
• 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.
• Langford, Michael J. 1973. Basic Photography. 3rd ed. Garden City, NY: Amphoto. ISBN 0-8174-0640-9
• Larmore, Lewis. 1965. Introduction to Photographic Principles. 2nd ed. New York: Dover Publications, Inc.
• 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/.
• ———. 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
• ———. 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
• ———. 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

 قراءات أخرى

• Hummel, Rob (editor). 2001. American Cinematographer Manual. 8th ed. Hollywood: ASC Press. ISBN 0-935578-15-3

 وصلات خارجية

• Depth of Field explanation and comparison photographs
• Depth of Field—the Third Dimension
• DOFMaster Depth of field calculator
• DOFMaster Explanation of why “all focal lengths have approximately the same depth of field” only under certain conditions
• DOFWizard Depth of Field software calculator for iPhone
• Luminous Landscape demonstration that all focal lengths have approximately the same depth of field when f-number and subject image size are maintained
• Carl Zeiss Depth of Field and Bokeh. Camera Lens News #35. April 2010. Accessed 2010-04-13.
• Bob Atkins’s Digital Depth of Field
• Bob Atkins’s DOF and Background Blur Calculator
• Jeff Conrad’s Depth of Field in Depth (PDF). Includes derivations of most DoF formulas
• Joe Englander’s Apparent Depth of Field: Practical Use in Landscape Photography (PDF). Alternative criteria for circle of confusion
• David Jacobson’s Photographic Lenses Tutorial
• Rik Littlefield’s An Introduction to Extended Depth of Field Digital Photography
• Dick Lyon’s Depth of Field Outside the Box (PDF). A format-independent look at DOF
• Justin Snodgrass’s Depth of Field Explained Video.
• Paul van Walree’s Depth of field.
• Paul van Walree’s DOF with Pupil Magnification. Includes derivation
• Kurt Wirz's Depth of Field (Focus stacking)