Depth Of Field

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A discussion on cinematography and the relationship between light and focal length. Circle of confusion is also considered

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  • MONSTERS:
  • Depth Of Field

    1. 1. CINEMATOGRAPHY (extending Aesthetics with theory)
    2. 2. DEPTH OF FIELD A Beginners Guide
    3. 3. This term usually brings up "circles of confusion" around people's eyes. But this does not need to be the case as it is actually rather simple. Depth of field defines the distance range where things have an acceptable level of sharpness. Although sharpness is very subjective, it is in general based on an 8" x 10" print viewed from a one feet distance. You can, for instance, define that an 8" x 10" print is sharp until you can still distinguish 4 lines per mm. That would represent dots of 0.25mm each or 100 dots per inch (DPI), a fair approximation. Other areas of the image would of course be sharper. In other words, 0.25mm or 250 µ (micron) is the cut-off point where we decide things are no longer sharp and is called the Maximum Permissible Circle of Confusion. An 8" x 10" print measures 203mm x 254mm and has a diagonal of 325mm, while 35mm film measures 36mm x 24mm and has a diagonal of 43.27mm or 7.5 times smaller. Since 35mm film needs to be enlarged 7.5 times to obtain an 8" x 10" print from it, the diameter of the Maximum Permissible Circle of Confusion must be 7.5 times smaller or 0.25/7.5 = 0.033mm. If you use 8" x 10" large format film, then the CoC remains at 0.25mm as the information on the negative does not need to be enlarged to create a an 8" x 10" print
    4. 4. DEPTH OF FIELD A Beginners Guide What is Depth of field ? DOF is simply said a distance range in which the objects appears to be in focus. Large DOF means that area is larger and more of the scene will appear in focus. Shallow DOF means the range will be smaller and objects closer or further will appear blurred.
    5. 5. DEPTH OF FIELD A Beginners Guide
    6. 6. DEPTH OF FIELD A Beginners Guide What affects Depth of field ? LIGHT FOCAL LENGTH (Aperture)
    7. 7. DEPTH OF FIELD A Beginners Guide What affects Depth of field ? ap·er·ture (pr-chr) n. 1. An opening, such as a hole, gap, or slit. 2.a. A usually adjustable opening in an optical instrument, such as a camera or telescope, that limits the amount of light passing through a lens or onto a mirror. b. The diameter of such an opening, often expressed as an f-number
    8. 8. DEPTH OF FIELD A Beginners Guide What affects Depth of field ? F-STOP/NUMBER Small Number = more light High Number = less light
    9. 9. DEPTH OF FIELD A Beginners Guide What affects Depth of field ? F-STOP/NUMBER Small Number = more light High Number = less light
    10. 10. DEPTH OF FIELD A Beginners Guide What affects Depth of field ? NEUTRAL DENSITY FILTER
    11. 11. DEPTH OF FIELD A Beginners Guide What affects Depth of field ? NEUTRAL DENSITY FILTER “ A piece of glass that affects the amount of light entering the lens but doesn’t affect the colour temperature”
    12. 12. DEPTH OF FIELD A Beginners Guide What affects Depth of field ? NEUTRAL DENSITY FILTER
    13. 13. DEPTH OF FIELD A Beginners Guide SELECTIVE FOCUS “ Used to call attention to the main action and deemphasize less significant parts of the frame and utilise differing focal planes”. Gamechanger - CITIZEN KANE 1941.
    14. 14. DEPTH OF FIELD A Beginners Guide DIFFERING FOCAL PLANES “ Placement of different articles on different distances from the lens”
    15. 15. DEPTH OF FIELD A Beginners Guide FOCUS PULLING (between differing focal planes) “…… becomes harder the less light you have coming through the lens”.
    16. 16. DEPTH OF FIELD A Beginners Guide EXAMPLE The use of different lenses and depths of field is something that we, as viewers take for granted. Watch the example and see how naturally depth of field and focal length are used.
    17. 17. DEPTH OF FIELD A Beginners Guide LENSES “ Major productions tend to use a variety of lenses to deliver differing depths of field”. Due to financial constraints you HAVE to think about what you are doing with what you have. Move your camera differing distances from your subject in order to experiment with DOF…..and watch the magic come alive
    18. 18. DEPTH OF FIELD A Beginners Guide RECAP ND Filter -………is and does what? What affects depth of field? Further Reading – Film Art Chapter 5 ‘Cinematography’

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