Calculating distance from subject?

[takethislife5150]

Is there a way to calculate the distance from a subject based on the size of the subject in the frame, the focal length, and all that?

[wulf]

Do you know the size of the subject? If so, you can probably work out the distance based on comparing that with their size in the frame and the focal length, although any distortion near the edges of the frame will make this more tricky.

However, my question is why do you want to do this? I wonder if it is really the best solution to whatever conundrum you have in mind?

Wulf

[Mr Guy]

Yes, with an if.

No, with a but.


It's pretty much impossible to do completely accurately from a single image. It's only even possible to do rough estimate from certain photographs and requires a lot of additional information, including reference points, known sizes, ability to prove something overlaps, etc...

You can come up with a pretty good estimate from exploiting parallax if you happen to have TWO images taken from different vantage points.

[takethislife5150]

Originally Posted by wulf

Do you know the size of the subject? If so, you can probably work out the distance based on comparing that with their size in the frame and the focal length, although any distortion near the edges of the frame will make this more tricky.

However, my question is why do you want to do this? I wonder if it is really the best solution to whatever conundrum you have in mind?

Wulf

curiosity really

[wulf]

If you are really curious, the best way is to go out, take some test shots and do some measuring and mathematics to see if you can figure it out. Let us know what you find out!

Wulf