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I want to calculate the camera's tilt angle from a photograph, without knowing anything about the camera (or lens). Suppose I can extrapolate the vanishing points (one-point or two-point perspective):

enter image description here

enter image description here

Is it possible to determine the tilt angle? Perhaps by measuring the distance between the vanishing point(s) and the centre of the image?

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  • What you conclude is correct for all normal (f-tan-theta) lenses. If you use a telecentric (f-theta) lens, perspective is distorted which complicates this approach. Check out the subject of photogrammetry for deriving quantitative data about this. – Stan Apr 7 '18 at 20:41
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    I'm voting to close this question as off-topic because it is about using a camera as a measuring device to accomplish another task, rather that about producing artistic photos. – Michael C Apr 7 '18 at 21:21
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In my opinion, the best way to do this is using a 3D program.

Sketchup has a special feature to mark the vanishing points of an image and that sets the camera position.

https://help.sketchup.com/es/article/3000115

The image is from Sketchup webpage.

enter image description here

On Blender there is an addon to do this. It is explained on this video: https://youtu.be/nb6rSMAooDs?t=2m16s

And the addon is here: https://github.com/stuffmatic/blam

Once you find the vanishing points, the horizon which is the line between them establishes the position of "eye-level" or the actual "elevation" of the camera lens. Use that as valuable information to establish "tilt" angle of camera.

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    FYI: Once you find the vanishing points, the horizon which is the line between them establishes the position of "eye-level" or the actual "elevation" of the camera lens. Use that as valuable information to establish "tilt" angle of camera. – Stan Apr 8 '18 at 16:26
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Clearly you would need to be making some assumptions about what is level and perpendicular to that, etc. Your assumption will be that buildings (or trees?) don't lean, and possibly other such assumptions. If you really need to know that angle, there are rigs that will record such details for you, along with GPS data.

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