[ptx] HFOV, focal distance...

[Bruno Postle]

On Fri 03-Jun-2005 at 15:06 +0200, Terje Mathisen wrote:

[a, b & c parameters]

> I measured it by printing a really big rectangular spreadsheet on 
> an A0+ printer, i.e. the printout is about 1.4 x 1.0 m.
>
> I then took a photo of this printout, after placing the camera on 
> a tripod and using a small mirror to make sure that the camera was 
> pointing at the actual center of the image.

This isn't strictly necessary, the rectangular grid object can be at 
any angle to the camera and you will still get accurate results.

> On the single image I placed 100+ horizontal and vertical line 
> control points, then optimized everything (y,p,r,a,b,c) 
> (remembering to select rectiliear output!) except HFOV.

This technique can actually determine the horizontal field of view 
at the same time as everything else, though if you want a really 
accurate value you do need to assemble a full 360 degree panorama.

-- 
Bruno