Note: "Focal distance" not "focal length (of the lens).
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22 Jun 17
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13 Oct 16
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the circle of confusion is actually smaller than the resolution of your screen for the two dots on either side of the focal point
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CONTROLLING DEPTH OF FIELD
Although print size and viewing distance influence how large the circle of confusion appears to our eyes, aperture and focusing distance distance are the two main factors that determine how big the circle of confusion will be on your camera's sensor.
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f/8.0
f/5.6
f/2.8note: images taken with a 200 mm lens (320 mm field of view on a 35 mm camera)
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Longer focal lengths may also appear to have a shallower depth of field because they enlarge the background relative to the foreground (due to their narrower angle of view). This can make an out of focus background look even more out of focus because its blur has become enlarged. However, this is another concept entirely, since depth of field only describes the sharp region of a photo — not the blurred regions.
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On the other hand, when standing in the same place and focusing on a subject at the same distance, a longer focal length lens will have a shallower depth of field (even though the pictures will frame the subject entirely differently). This is more representative of everyday use, but is an effect due to higher magnification, not focal length.
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The key concept is this: when an object is in focus, light rays originating from that point converge at a point on the camera's sensor. If the light rays hit the sensor at slightly different locations (arriving at a disc instead of a point), then this object will be rendered as out of focus — and increasingly so depending on how far apart the light rays are.
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Why not just use the smallest aperture (largest number) to achieve the best possible depth of field? Other than the fact that this may require prohibitively long shutter speeds without a camera tripod, too small of an aperture softens the image by creating a larger circle of confusion (or "Airy disk") due to an effect called diffraction — even within the plane of focus.
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18 Jul 16
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In fact, everything immediately in front of or in back of the focusing distance begins to lose sharpness
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When the circle of confusion becomes perceptible to our eyes, this region is said to be outside the depth of field and thus no longer "acceptably sharp." The circle of confusion above has been exaggerated for clarity; in reality this would be only a tiny fraction of the camera sensor's area.
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When does the circle of confusion become perceptible to our eyes? An acceptably sharp circle of confusion is loosely defined as one which would go unnoticed when enlarged to a standard 8x10 inch print, and observed from a standard viewing distance of about 1 foot.
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camera manufacturers assume a circle of confusion is negligible if no larger than 0.01 inches (when enlarged)
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aperture and focusing distance distance are the two main factors that determine how big the circle of confusion will be on your camera's sensor
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the total depth of field is virtually* constant with focal length
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Note how there is indeed a subtle change for the smallest focal lengths. This is a real effect, but is negligible compared to both aperture and focusing distance. Even though the total depth of field is virtually constant, the fraction of the depth of field which is in front of and behind the focus distance does change with focal length, as demonstrated below:
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This exposes a limitation of the traditional DoF concept: it only accounts for the total DoF and not its distribution around the focal plane, even though both may contribute to the perception of sharpness. Note how a wide angle lens provides a more gradually fading DoF behind the focal plane than in front, which is important for traditional landscape photographs.
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Longer focal lengths may also appear to have a shallower depth of field because they enlarge the background relative to the foreground (due to their narrower angle of view). This can make an out of focus background look even more out of focus because its blur has become enlarged
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Depth of field also appears shallower for SLR cameras than for compact digital cameras
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Another implication of the circle of confusion is the concept of depth of focus (also called the "focus spread"). It differs from depth of field because it describes the distance over which light is focused at the camera's sensor, as opposed to the subject:
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The key concept is this: when an object is in focus, light rays originating from that point converge at a point on the camera's sensor. If the light rays hit the sensor at slightly different locations (arriving at a disc instead of a point), then this object will be rendered as out of focus — and increasingly so depending on how far apart the light rays are.
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04 Feb 16
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02 Feb 16
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aperture and focusing distance distance are the two main factors that determine how big the circle of confusion will be on your camera's sensor
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Note how there is indeed a subtle change for the smallest focal lengths. This is a real effect, but is negligible compared to both aperture and focusing distance.
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Another implication of the circle of confusion is the concept of depth of focus (also called the "focus spread"). It differs from depth of field because it describes the distance over which light is focused at the camera's sensor, as opposed to the subject:
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"circle of confusion" is used to define how much a point needs to be blurred in order to be perceived as unsharp
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The key concept is this: when an object is in focus, light rays originating from that point converge at a point on the camera's sensor. If the light rays hit the sensor at slightly different locations (arriving at a disc instead of a point), then this object will be rendered as out of focus — and increasingly so depending on how far apart the light rays are.
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Although print size and viewing distance influence how large the circle of confusion appears to our eyes, aperture and focusing distance distance are the two main factors that determine how big the circle of confusion will be on your camera's sensor. Larger apertures (smaller F-stop number) and closer focusing distances produce a shallower depth of field. The following test maintains the same focus distance, but changes the aperture setting
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Note that focal length has not been listed as influencing depth of field, contrary to popular belief
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If the subject occupies the same fraction of the image (constant magnification) for both a telephoto and a wide angle lens, the total depth of field is virtually* constant with focal length!
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10 Sep 15
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Although print size and viewing distance influence how large the circle of confusion appears to our eyes, aperture and focusing distance distance are the two main factors that determine how big the circle of confusion will be on your camera's sensor. Larger apertures (smaller F-stop number) and closer focusing distances produce a shallower depth of field. The following test maintains the same focus distance, but changes the aperture setting:
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Depth of field refers to the range of distance that appears acceptably sharp
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CLARIFICATION: FOCAL LENGTH AND DEPTH OF FIELD
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It varies depending on camera type, aperture and focusing distance,
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Depth of field refers to the range of distance that appears acceptably sharp
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circle of confusion" is used to define how much a point needs to be blurred in order to be perceived as unsharp.
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depth of field only sets a maximum value for the circle of confusion, and does not describe what happens to regions once they become out of focus. These regions are also called "bokeh
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Note that focal length has not been listed as influencing depth of field, contrary to popular belief.
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09 Sep 15
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The depth of field does not abruptly change from sharp to unsharp, but instead occurs as a gradual transition.
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aperture and focusing distance distance are the two main factors that determine how big the circle of confusion will be on your camera's sensor. Larger apertures (smaller F-stop number) and closer focusing distances produce a shallower depth of field.
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Note that focal length has not been listed as influencing depth of field, contrary to popular belief.
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Even though the total depth of field is virtually constant, the fraction of the depth of field which is in front of and behind the focus distance does change with focal length
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In order to calculate the depth of field, one needs to first decide on an appropriate value for the maximum allowable circle of confusion. This is based on both the camera type (sensor or film size), and on the viewing distance / print size combination.
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depth of focus
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It differs from depth of field because it describes the distance over which light is focused at the camera's sensor, as opposed to the subject:
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The key concept is this: when an object is in focus, light rays originating from that point converge at a point on the camera's sensor. If the light rays hit the sensor at slightly different locations (arriving at a disc instead of a point), then this object will be rendered as out of focus — and increasingly so depending on how far apart the light rays are.
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effect called diffraction
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macro photography
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providing visual proof that depth of field does not change much with the focal length.
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08 Sep 15
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The depth of field does not abruptly change from sharp to unsharp, but instead occurs as a gradual transition. In fact, everything immediately in front of or in back of the focusing distance begins to lose sharpness — even if this is not perceived by our eyes or by the resolution of the camera.
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TUTORIALS: DEPTH OF FIELD
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Matt CDepth Of Field
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The depth of field varies depending on camera type, aperture and focusing distance
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0.01 inch
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0.01 inch standard
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Add Sticky Noteaperture and focal distance are the two main factors that determine how big the circle of confusion will be on your camera's sensor
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Note that I did not mention focal length as influencing depth of field. Even though telephoto lenses appear to create a much shallower depth of field, this is mainly because they are often used to make the subject appear bigger when one is unable to get closer. If the subject occupies the same fraction of the image (constant magnification) for both a telephoto and a wide angle lens, the total depth of field is virtually* constant with focal length! This would of course require you to either get much closer with a wide angle lens or much further with a telephoto lens, as demonstrated in the following chart:
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Longer focal lengths also appear to have a shallow depth of field because they flatten perspective. This renders a background much larger relative to the foreground-- even if no more detail is resolved. Depth of field also appears shallower for SLR cameras than for compact digital cameras, because SLR cameras require a longer focal length to achieve the same field of view.
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In order to calculate the depth of field, one needs to first decide on an appropriate value for the maximum allowable circle of confusion. This is based on both the camera type (sensor or film size), and on the viewing distance / print size combination.
Depth of field calculations ordinarily assume that a feature size of 0.01 inches is required for acceptable sharpness (as discussed earlier), however people with 20-20 vision can see features 1/3 this size. If you use the 0.01 inch standard of eyesight, understand that the edge of the depth of field may not appear acceptably sharp. The depth of field calculator below assumes this standard of eyesight, however I also provide a more flexible depth of field calculator.
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Add Sticky Note
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Canon SX20 fully zoomed, 100mm, has f/5.7. If focused at 75m, acceptably sharpness is 60m-100m, or 40m range.
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If focused at 10m, 9.7m-10.3m, .6m range.
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If subjecct size in the image is kept the same by moving the closer or further away, the DOF is constant, regardless of the lens focal length.
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I confirmed this using the DOF Calculator in this article. For example, at f/4, the DOF is 0.116m if the subject distance is inversely proportional to the focal length, which is hat is required for a constant subject size.
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Michael GwytherDepth of field is the range of distance around the focal plane which is acceptably sharp. The depth of field varies depending on camera type, aperture and focusing distance, although print size and viewing distance can influence our perception of it.
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EPTH OF FIELD -
Depth of field is the range of distance around the focal plane which is acceptably sharp. The depth of field varies depending on camera type, aperture and focusing distance, although print size and viewing distance can influence our perception of it. This section is designed to give a better intuitive and technical understanding for photography, and provides a depth of field calculator to show how it varies with your camera settings.
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pvav pvavDepth of field is the range of distance around the focal plane which is acceptably sharp. The depth of field varies depending on camera type, aperture and focusing distance, although print size and viewing distance can influence our perception of it.
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Public Stiky Notes
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