June 20, 2016 at 8:06PM

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If I convert from Sony A7Sii S-Log3 XAVC footage to ProRes (LT and higher), will I lose the flexibility in the colouring stages if I were to grade in ProRes?

I asked this over on Reddit , but I'm expanding my search for answers over here!

I prefer to edit, grade and finish in ProRes in Premiere CC, simply because it's much smoother and easier on my system. I work with a travel adventure Youtube channel and we have lots of footage. I choose to work with ProRes in Premiere CC because I find that working with lots of files in different formats and codecs really bogs Premiere down (waiting for thumbnails to load really gets me frustrated). I also find that editing ProRes, doing some light color grading, and EXPORTING from ProRes in Premiere a huge timesaver because I don't have to do any relinking.

Anyway, my question here is: Does converting to ProRes 'flatten' the colour data from S-Log3 XAVC footage?

Here's what I was thinking as well:
SONY footage at XAVC-S: 1920 x 1080p / 59.94 fps (50 Mbps)
Apple ProRes LT: 1920x1080p / 59.94 fps (approx. 294 Mbps)

This might be a wrong way of thinking, but wouldn't converting to a higher data rate codec retain the colour information?

Looking to get some definitive answers if possible!

14 Comments

No, you won't lose anything. Almost everybody (on Macs) converts from whatever their camera shoots to ProRes as a pro intermediate format.

XAVC and ProRes are two different codecs. They have nothing to do with S-Log3 or Rec709 (which are gamma curves and possibly color matricies). Convert XAVC to ProRes, treat it like it's S-Log3, and you are off to the races.

June 20, 2016 at 9:48PM

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This guy RIGHT HERE. This guy.

Chuck 'im a carrot n 'alf!

David Dearlove

June 21, 2016 at 1:51PM

Thanks for sharing this vital information!

Joshua Laplap

June 23, 2016 at 4:38AM

Colorwise it won't change anything as Prores is 422 8 or 10bit, although it will change a bit on fine detail in very complex image, if you have a fix shot of grass for instance as prores compress frame by frame it is not able to keep as much detail as xavc.
But if you air on youtube in the end it doesn't change much as youtube compression is very strong anyway.

June 21, 2016 at 7:43AM, Edited June 21, 7:43AM

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AvdS
1179

And the result pretty much dictates my process, unfortunately. I work with a Youtube channel and our footage plays there pretty much exclusively.

My workflow currently goes:
- Import original files to storage
- Transcode files to ProRes
- Edit, grade and export in ProRes

Joshua Laplap

June 23, 2016 at 4:38AM, Edited June 23, 4:38AM

Joshua, other than a faster export time, is there a benefit to exporting in ProRes before uploading to Youtube? Youtube compression is essentially converting the footage to h.264

Giovanny Lago

June 23, 2016 at 7:14PM

Umm what?! ProRes being Intra-Frame should retain complex image detail better!

Nate O

December 13, 2016 at 8:15AM, Edited December 13, 8:15AM

You will not loose color information, you are not gaining information either. You are starting with a compressed codec and changing it to another codec. It won't be as compressed, but you don't gain detail or color or anything else, you are just making it so that your computer doesn't have to work as hard to playback footage.

June 21, 2016 at 11:35AM

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Eric Buist
Producer | Creator
481

Yeah, the biggest reason for transcoding is that I hate any form of stutter when editing. And wow... XAVC and H264 footage really slows down Premiere like crazy. Having lots of native footage really grinds my gears...

Thanks for your explanation.

Joshua Laplap

June 23, 2016 at 4:36AM

What people have said here is true - going from a heavily compressed 8-bit XAVC to less-compressed ProRes (8 or 10 bit) will be a virtually lossless process, including the "unseen" data (highlight/shadow detail and color leeway). Think of it as pouring your glass of water (XAVC) into a bucket (ProRes). You won't spill any, and the bucket is much easier to move around without spilling any.

But for the sake of thoroughness, note that this is a VIRTUALLY lossless process - any de-compression and re-compression of data can only give you less than you started with. Think of this as the drops that still remain on the inside of your glass after you pour. Insignificant, but there.

June 22, 2016 at 9:50PM, Edited June 22, 9:50PM

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Thank you, fam. This is all very useful information. Now I'm thirsty for some water.

Joshua Laplap

June 23, 2016 at 4:34AM

As most comments have already mentioned, your XAVC footage, has already been compressed. Transcoding it to a Codec with less compression, ProRes, will not return data lost during the initial recording.

What you will gain is the difference from an Inter-frame Codec (XAVC/h.264) to a Intra-frame Codec (ProRes). Intra-frame is a lot more friendly to you system.

http://www.leckman.com/articles/codecs_05.html

Alternatively, if you were to use an external recorder with your A7s, then you would bypass the internal compression, thus gaining more data for use in POST then what you have now ... and no waiting for a transcode!

July 13, 2016 at 4:55PM

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John Dimalanta
Freelance Photographer/Cinematographer
455

Just FYI Joshua, XAVC-S is just a specific version of h.264. I know that 1080p24 from an A7S is:
High Profile Level 4.1
GOP = 6 (keyframe every 6)
2 B-Frames

Pretty certain this stays the same for every frame rate on an A7S(II).

July 14, 2016 at 3:59PM

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You won't lose much converting to ProRes and you won't lose any color. I would say if possible, consider getting an external recorder to record S-Log from the camera straight to ProRes, I honestly think that is the best way to go. Sort of like how the Arri Alexa has ProRes. There motto early on and still is I believe "shoot > edit" which describes how easy it can be perfectly when you start with ProRes.

December 13, 2016 at 8:23AM

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Nate O
Cinematographer/Video Editor
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