# How do i find the distance required to resolve a point on a page from a mobile camera?

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 ?

• 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? Sep 8, 2019 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 Sep 9, 2019 at 14:01
• Possible duplicate of What is the farthest a camera can see? Sep 9, 2019 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. Sep 9, 2019 at 16:32

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.

• I am more concerned about the theoritical physics behind this measurement Sep 9, 2019 at 14:04