Other: Losing quality and coloris if converting Slog3 to other formats ?

[Gogu]

Hello,

I would like to know if dynamic range or colors get shifted/modified in a bad way if I convert my footage from the original XAVC files of the FS7 to an intermediate high quality codec.
The reason I want to do this is that I'm doing cc work in Speedgrade and unfortunately if only accepts .mov not mfxs, I'm using it as a standalone application and not through Direct Link through Premiere because it is much more stable and fast.

I'll transcode my footage to either Cineform or Dnxhd. I suppose 10-bit option is a must but other than that is there any problem with doing this ?
I did some tests and the footage looks 99% identically inside a Premiere timeline, comparing original footage with the 2 above mentioned codecs, without any LUT applied.
It would probably look the same if I convert it to a simple h264 format, that's why I am asking. Even I do don't see it with my eyes does the color science inside the file gets screwed up somehow when converting ?

Personally I'm pretty sure nothing can get corrupted since sLog is just a mathematical formula that gets put in the file, but I'm not convinced about the color gamut part !
Thanks.

 

[starcentral]

75% of the time I transcode footage from 10-bit XAVC to ProRes 422. Sometimes 422 HQ, but rarely.

My opinion and experience is that since ProRes 422 has a higher data-rate than the originating XAVC does, the quality should generally be higher.

Truth is you can always compare codecs this way, but again from my experience 422 or 422 HQ is higher than native XAVC.

I've also used H.264 in the past on the highest quality setting from Davinci Resolve to transcode XAVC to H.264 and the results weren't bad but this is not a great codec to use for this in reality.

If you are on Windows then you can use DNxHD 10-bit and it's great as well.


As for slog and color etc.. slog3 is just a gamma curve that doesn't really affect color as much as the color space of the file. I wouldn't be too concerned about conversion but know that if you are giving files to someone for GRADING purposes that you should give them the SLOG versions not converted to some REC709 look or something, that will really limit them in the grade.

cheers,