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Phantom 3 camera focus distance

Discussion in 'Phantom 3 Help' started by virtue, May 16, 2015.

  1. virtue

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    I have ordered a P3, and want to use it mostly for still photography. While the camera is obviously capable of taking some really stunning photos, it's going to take some getting used to a camera with a fixed focal length, fixed focus distance, and a fixed aperture. The fixed (wide open) aperture and focus at infinity will mean some loss of sharpness at close quarters. I know this is not exactly how most people want to use the P3, but it would be nice to be able to take close-in photos when needed.

    My question is this. An f2.8 20 mm focal length (35 mm format equivalent) lens focused at infinity will have a near depth of field distance of around 24 feet - i.e. subjects this close will still be sharp. The same lens with a focus point at 24 feet, will have a depth of field that extends from around 13 feet to infinity. My reading of the P3 specs is that the former is true - the focus point is actually infinity. Would it not make more sense to set it at 24 feet (the 'hyperfocal' distance)? Or do I have it wrong - the lens is designed to focus on the hyperfocal point, thus providing the maximum depth of field that includes infinity?

    Has anyone run tests to determine how close a subject can be to the camera, and still be in sharp focus?
     
  2. Rexian

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    I plan to find that out myself once it arrives. Mine is expected to ship this week. Pretty much every smartphone now a days has autofocus so not sure why a dedicated camera doesn't. Maybe they don't want the subject to go out of focus every now and then... and then cost.
     
  3. Meta4

    Meta4 Moderator
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    Your phone has a focusing lens because you use it for scenery as well as portraits and close-up.
    Two reasons the Phantom camera has no focus.
    1. Weight and complexity .. DJI have pioneered the dedicated aerial camera and weight is a critical factor
    2. Being an aerial camera, you are very rarely going to have your subject up close. Almost never closer than 20 ft and usually hundreds of feet away. The lens has a very wide field of view and this gives it a very good depth of field. Because of this focus is unnecessary.
    Your subject won't go out of focus - because it's always in focus.​
     
  4. dhaslam

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    I photographed the P3 quick start guide at 3', 4' and 5' with the P3A camera. The text was not fully readable at any of the distances but the best was at 3' and at that distance the column headings were readable. So I would say that the nearest focusing distance is about 3'. I took the same photograph with a zoom lens set at 20mm on a full frame Sony camera and the result was almost identical.
     
  5. dhaslam

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    This calculator below gives a hyperfocal distance of 2.8' for a range from 1.4' to infinity in focus. I am assuming that the LMF is 5.62 and the lens focal length is 3.6mm. With the lens focused at infinity the image at 3' should be sharp and it is sharp. It compares favourably to the result from a 35mm lens costing the same as the P3.

    http://www.outsight.com/hyperfocal.html
     
  6. Rexian

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    True in most cases, but it will show when any subject with details captured at a short distance.