Well, that's weird. Maybe it depends on map dimensions then. my last map, where I managed to use 16-bit tiff was a 6 x 12 in spring, that makes it 3072 x 6144 pixels large in texture map (scaled to 1844 x 4097 before import to Carrara). There the raw method didnt work at all, I got an import failed-error.
Now with another map, with spring dimensions 12 x 10 and a texture map with the dimensions 6144 x 5120 pixels gives me other results: now I don't get the import failed errors but instead the tif-map is imported as flat (also commented in
this) forum). Raw and photoshop formats give me weird results, basically another map than what I made, also depending on the dimensions (if scaled to a 4097 x 3414 or 2049 x 1707 pixels before importing to carrara).
Here are some examples:
1) TIFF-format, 8-bit, dimensions 4097 x 3414. Result: as expected. When rendering gets scanlines though.
2) TIFF-format, 16-bit, dimensions 4097 x 3414. Result: flat
3) Raw-format, 16-bit, dimensions 4097 x 3414, Intel byter order, header 0. Result: scrambled
4) Photoshop format, 16-bit, dimensions 4097 x 3414. Result: Interesting (but altered heightmap)
5) Photoshop format, 16-bit, dimensions 2049 x 1707. Result: scrambled.
6) PNG-format, 16-bit, dimensions 4097 x 3414. Result: as expected (but may not be optimum for rendering)
So for this heightmap, the png-format was the only 16-bit format that worked for me. Hopefully this detectiove work is of use to someone else too (I like detective work).