[Tom Daigon] "if there's a preview file, it decodes the frame out of it, & re-encodes it into the final file. So while it'll help in (non-CUDA) effects heavy compositions, it also incurs a generation loss. Generally, we don't recommend using it (hence the default to off) unless you really are sure that's what you want.""
I'm not at all sure that this is true in all cases.
I usually render my previews to a Matrox codec @ 200mbps. Exports to the same codec and bit depth go extremely fast and I've noticed no quality loss. However, I must admit I haven't put the two side by side under a microscope. If I'm working with heavy effects renders that have lots of gradients I render previews at 10 bit uncompressed which will avoid any potential generation loss rendering with previews to final outout. If my output needs to take up less space than a 10 bit uncompressed file I'll go to a less storage intensive codec (AVCIntra
@100mbps or Matrox iframe
@200mbps) and see minimum quality loss.
David
AllinOneFilms.com
