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Given all details such as focal length , aperture etc , how can i find the size of a point on a paper that is at a given distance from a mobile camera ? Or vica versa , the distance required to resolve a point of a given size ?

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  • I think I know what you mean, but a point by definition has no size. Can you more exactly describe what you want to know?
    – mattdm
    Sep 8 '19 at 23:18
  • @mattdm I am considering a point from a practical aspect . Take it to be a 10x10 px picture on a laptop screen
    – Puja Dhinchak
    Sep 9 '19 at 14:01
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    Possible duplicate of What is the farthest a camera can see?
    – mattdm
    Sep 9 '19 at 16:31
  • Since you note in a comment that what you want is the purely-theoretical limit, see the answer about diffraction limits in the previous question linked above.
    – mattdm
    Sep 9 '19 at 16:32
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Experimentally:

  • Take a picture of a sheet of ruled/squared paper.
  • Open the photo in an image viewed/editor
  • Measure the distance in pixels between two lines
  • Divide the physical distance (in mm/inches...) between two rules by half that value. This will give you an estimate of the smallest thing you can see in a picture, if the lens is good enough for the sensor.

You can also find lens test charts on the web that may tell you a bit more about your camera.

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  • I am more concerned about the theoritical physics behind this measurement
    – Puja Dhinchak
    Sep 9 '19 at 14:04
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    @PujaDhinchak Then ask in Engineering...
    – xenoid
    Sep 9 '19 at 14:15
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No. You can't know this from the technical specs you are thinking of. The resolving power of a camera system depends on the way the lens is built and the properties of the recording medium — and other factors such as lighting and atmosphere.

You may be able to get some details of the recording medium — the sensor — from camera specs, but not enough to be really useful in practice. And for lenses, the resolving power is characterized by testing, not calculated in theory.

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  • I want to know the physics/calculations behind . Please ignore all practical factors that can affect it . Eg ignore air refractive index , lens quality . Take everything ideal\
    – Puja Dhinchak
    Sep 9 '19 at 14:03

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