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Given this formula for calculating the distance to an object as long as you have a picture of the object and know the actual height of the object...

distance to object (mm) = focal length (mm) * real height of the object (mm) * image height (pixels)
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                          object height (pixels) * sensor height (mm)

What would be an accurate range of ratios of Focal Length and Sensor Height to approximate a human eye?

I think this question is sufficiently different from this one... and this one...

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marked as duplicate by mattdm, NickM, Hugo, Michael C, Philip Kendall Oct 22 '15 at 8:47

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

  • I think you should use the resolution of the human eye to get started (and read this : cambridgeincolour.com/tutorials/cameras-vs-human-eye.htm) – Olivier Aug 26 '15 at 5:40
  • The part of the question if everything in the eye's FOV were at the best resolution an eye can provide makes little sens to me... What do you mean by that ? – Olivier Aug 26 '15 at 16:57
  • @Olivier - That was because people in the other questions were talking about how the eye's vision gets fuzzy outside of a small circle of vision. ... Nevermind that part... I'm deleting it... – Malady Aug 26 '15 at 22:24
  • Ok :) Is my answer enough or would you like more ? – Olivier Aug 27 '15 at 5:38
  • @Olivier - Yes, well, a actual value of FOV would be nice, but the fact that you've provided a method is very useful. – Malady Aug 27 '15 at 12:13
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Let's go for a "purely" mathematical reasoning.

Let's assume that the eye has a FOV = afov.

With ho an object height and hs the sensor height, d the distance to the object and f the focal length, you have the following schema :

relation between parameters

Finding a relation between all those values is straightforward : hs / f = tan(0.5* afov)

Unless I'm mistaken, you "just" have to settle for an estimation of the eye FOV to get your ratio.

Now, to get an estimation of an human's eye FOV, you can visit Biology SE, it says Monocular field of view (measured from central fixation) is 160 deg (width w) x 175 deg (height h), so afov = 175 deg.

This answer from mattdm might help too : https://photo.stackexchange.com/a/5924/26456 => For a human eye, the angle of view happens to be about 95°, but since your eyes move around unconsciously and your brain fills in the details, it feels much wider than that.

You can probably find other sources (and other values).

I let you compute the tangent value :)

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  • sorry but there is something not so clear for me in that formula. what is sensor height(mm) ? is it a value linked to the camera type? I ask this because I know another formula to find the distance: D’ = (W x F) / P where D'is the distance (mm), w is the Width (mm) of the object (in your case the height), and P the perceived width (pixel) of the object on the image – Edess Elder Oct 21 '15 at 1:57
  • Sensor height is the physical size of the sensor (different camera model = different sensor size, look at "crop factor"). To get a physical distance from pixels, you have to multiply the length of your object in pixels by the physical distance between two "pixels" on the sensor to get the physical size of the object's image on the sensor. – Olivier Oct 21 '15 at 20:34

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