Hi Götz Echtenacher
Preview -> only detected and used features are used for creating mesh
Normal -> Image downscale 2 is default, in many cases 3 or 4 are used for various reasons ( 50-250Mpix images ) so you can play a bit here.
High -> Image downscale 1x ( so NO downscale at all is used ) so if want use 2x 3x 4x then the NORMAL mode is here for changing settings…