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Camera Field of View / Focal Length Study


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I have had a long running problem getting the characters (from MakeHuman) to not look distorted, especially when you get the camera close.  I thought it was a BJS from Blender problem.  I recently found I was not the only one having the problem.  Turns out the problem originates in Blender.  In MakeHuman the camera is orthographic.  The response from punkduck in the link suggested switching the focal length from the Blender default of 35mm to 120mm.

BJS uses field of view, not focal length, but that seems to be the same thing just measured a different way.  Blender UI can switch between either unit:


A 35mm focal length is a 49.135 degree FOV (0.857556 radians).

A 120mm focal length is a 15.189 degree FOV (0.265103 radians).

BTW, default FOV is 0.8 radians.

On a scene I am working with today, I switched the function of a checkbox to toggle between 0.857556 & 0.265103.  0.265103 fixed my problem!!  Switching to 0.265103 effectively moves the camera much "closer", but adjusting so that the bust fills the same space, I took 2 snaps.  The first is 35mm & 2nd is 120mm.



I thought I would start this topic to try to discover the implications of this.  Is this just a MH issue?  What is the right FOV, especially for VR?  Why is the default 0.8?  Maybe some people could run scene.activeCamera.fov = 0.265103 on there scenes and report what they get.  Seems like a topic for a Friday / weekend.

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@JCPalmer : In photography, if I  remember correctly from my hobby days, these kind of focal lengths for portraits:

1. Full body: 50  to 85mm (towards lower end)

2. Head and shoulders : 85 mm

3.Tight face : 85 to 135mm (towards upper end).

So for your dude - it looks like you got a good answer by experimentation

cheers, gryff :)



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