In aerial photography, or photography in general: Is there a term for the point where the optical axis intersects the ground plane( scene)?


In engineering we call the optical center on the image plane "principal point". But that would be where the point you are looking for is projected. We dont have a name for that point in the natural domain.

  • Thank you! At least then I know I am not doing anything wrong in just creating a name for that point. – Tormod Haugene Dec 15 '13 at 8:04

I think what you are looking for is the focal plane or plane of focus, which is distinct from the image plane that contains the film or sensor recording the scene. However, not all scenes contain elements that are all the same distance from the camera. Even in aerial photography unless the optical axis is perpendicular to the ground then some parts of the scene will be different distances than others. This is usually overcome by using a narrow enough aperture to provide a fairly deep depth of field.

  • I might have misunderstood my own question in that case. The word that I am looking for will be identical to the ground nadir for a vertical photo; that is, the point on the ground in the middle of the photo, seen through the camera. For a non-vertical photo, what would the equivalent to "ground nadir" be? – Tormod Haugene Dec 13 '13 at 19:57
  • @TormodHaugene - Maybe just a "center point", when you look at the photograph. I guess you must mean the point in the subject area, for example in a landscape photo you might have a certain tree in the center point. I have not heard a name for that point, but perhaps technical photography, machine vision, or suchlike, has a name for it. We are a bit on the artistic side of photography here :) – Esa Paulasto Dec 14 '13 at 12:04
  • Okey! Well, thank you for you help. I guess I will just give it some name then.. :) – Tormod Haugene Dec 14 '13 at 12:57
  • @Tormod: In normal photography, there isn't anything that corresponds with a "ground nadir" as in arial photography. Depending on where your subjects are in the scene, there could be multiple points across the area of the frame where important subjects are in clear focus. Those points will not necessarily be in the center of the frame, either. All there really is is the focal plane, the point within the real-world scene where optical focus is sharp enough to not otherwise be determined as out of focus, and that all depends on the aperture. – jrista Dec 14 '13 at 16:08

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