Hallöchen!
Iain Wood writes:
> [...]
>
> Using this method gives un-natural distortion near the
> corners. Fish-eye hemi preserves shapes outside the central
> area. This is most obvious with faces.
All projections make compromises. Lensfun’s projections are
optimised for architectural photography. If you want to preserve
faces, you may use stereographic projection, however, this does not
yield straight vertical lines.
Fisheye-hemi uses cylindrical projection. You can simulate it with
the following patch in Lensfun:
diff --git a/libs/lensfun/mod-coord.cpp b/libs/lensfun/mod-coord.cpp
index c435756a..aa20e21a 100644
--- a/libs/lensfun/mod-coord.cpp
+++ b/libs/lensfun/mod-coord.cpp
@@ -868,7 +868,7 @@ void lfModifier::ModifyCoord_Geom_ERect_Rect (void *data,
float *iocoord, int co
float x = iocoord [0];
float y = iocoord [1];
- double phi = x * inv_dist;
+ double phi = asin (x * inv_dist);
double theta = -y * inv_dist + M_PI / 2.0;
if (theta < 0)
{
Then, select "equirectangular", and you get cylindrical instead.
This plus perspective correction seems to yield Fisheye-hemi’s
results, however, without the new Lensfun supported by DT, I cannot
realy tell. FWIW, I get *very* close without PC already.
This could mea to add the cylindical projection to Lensfun. It
would be good to make more tests, though.
Tschö,
Torsten.
--
Torsten Bronger
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