Affect of aspect ratio and cropping on 1080 3D movie

[iridius]

I read a thread that said I could adjust aspect ratio and crop to watch a SBS 3D movie on a normal screen.

If I do this to a 1080p 3D movie, will it effectively make it half quality or 540p (if that even exists)?
I don't have a 3D screen or glasses, but would like to future-proof (as much as possible) my downloads by downloading 1080p 3D movies (as they seem to be the latest & greatest), but if it is halving the quality in my scenario, then I'll just stick to regular 1080p videos.

Thanks

[iridius]

Is this a dumb question, or just unanswerable, or maybe just uninteresting