"but if I load a texture with the flag 512 then it shows perfectly and I'm still running in 16bit, so
how is it possible that?"
Textures are stored in 24bit format, and all 3D output is dithered. Dithering hides the banding, though only if you don't know to look for it. :-) If you look closely you will be able to see dots moving about rapidly as the dither pattern changes constantly to make it less obvious.
If you set Dither False in your program, then assuming dithering is not being forced on by the driver, you should be able to see the banding again. I did that in my tank game because I can't stand dithering.
2D output is not dithered, hence the bands being visible.
As for Luke's mach banding thing, I don't know anything about that, but I think I've heard the term before. What you're seeing is probably not mach banding though.
how is it possible that?"
Textures are stored in 24bit format, and all 3D output is dithered. Dithering hides the banding, though only if you don't know to look for it. :-) If you look closely you will be able to see dots moving about rapidly as the dither pattern changes constantly to make it less obvious.
If you set Dither False in your program, then assuming dithering is not being forced on by the driver, you should be able to see the banding again. I did that in my tank game because I can't stand dithering.
2D output is not dithered, hence the bands being visible.
As for Luke's mach banding thing, I don't know anything about that, but I think I've heard the term before. What you're seeing is probably not mach banding though.