[r0lZ]

Good question, robl45!

And I add that you cannot make a full-SBS without re-encoding, because the native BD3D format is AVC+MVC (two video streams encoded differently), and the format of Full-SBS is a single stream (with the two views side by side) encoded in pure AVC (or another format such as HEVC). Therefore, no, BD3D2MK3D cannot do that, but what you want cannot be done, with BD3D2MK3D or any other tool.

You can however re-encode with any CRF value, including CRF 0, meaning lossless. But the output file will be MUCH larger than the original BD, and you will probably be unable to store the final MKV on a standard HDD! Is it really what you want?

Note also that with a reasonable CRF value (say around 20), you will probably be unable to see the difference with the original (unless you use comparison tools to highlight the differences). Why do you want to waste disc space for a supposed high quality that your eyes are unable to see?

If you really want to keep the original video streams without re-encoding them, try MakeMKV. It can store the AVC and MVC streams in a single MKV, but only one or two software players are currently able to play the generated video in 3D. And of course, it's not Full-SBS. IMO, that solution is roughly equivalent to doing a backup of the original movie, but without a real possibility to watch it.