proj-imim:
RE: FoV versus focal length formula for fisheye lenses?
uwai 2001-Apr-24 16:03:10
Hi,
"fov" meant the angle from optical axis (0 to 90 degrees (= pi/2 rad) for
most circular fisheye) in the formula.
If a lens projects hemisphere to 23 mm diameter circle,
the f must be about 7.3 mm with equidistant projection.
Or 8.1 mm with equal area projection.
However, the commercial product is not necessarily filling the formula
completely.
Usefull link;
http://www.coastalopt.com/ne080400.htm
I think nikon 8mm F2.8, 6mm F2.8, 6mm F5.6, FC-E8 + E900 master lens are
designed as equidistant, while olympus 8mm F2.8, sigma 8mm F4(MF) are as
equal area.
Sorry for poor english.
Uwai
http://nagoya.cool.ne.jp/uwai
--- Joost Nieuwenhuijse <#removed#>$B$5$s$O=q$-$^$7$?!'(B
> Thanks.
> I guess the first is the most common? I've never heard of a 12mm
> fisheye
> giving 180 degrees coverage.
>
> Joost
>
> > Hello,
> >
> > w = f * fov (fov in radian) for equidistant projection.
> >
> > w = 2 * f * sin(fov/2) for equal area projection.
> >
> > Almost all fisheyes are designed as one of the two projections.
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