Pro Res Raw File Temperature Shift During Clip

Hello There,

First time poster so please be gentle. 

I am very new to using Pro Res Raw and I have a question.

My setup is Sony A7siii with external atomos ninja v recorder. 

I am sending RAW over HDMI and recording that on the ninja whilst simultaneously recording internally XAVC-S.

I have a scenario where I used AWB for a shot whilst recording in RAW. I know that’s not the best idea, but the shot started inside and ended outside in completely different light and so I just went with AWB

Here is the issue I am having 

if I look back at the raw clip in FCPX, there are 2 occasions where there is a clear color shift from cooler to warmer and then back again

If I look at the same clip that was recorded internally as XAVC-S that shift is not present. 

The shift is also not noticeable on either clip if viewed in QT, which is very possibly beside the point. 

The atomos was in native monitoring mode, no LUTS applied etc. 

is this simply as a result of using AWB?  If so, why does it not appear on the XAVC-S clip or am I doing something else wrong here. 

I apologize if this is a very simple question and I appreciate any insights you have. 

Thanks,

Chris. 

I *think* this may be what's happening: Similar to in-camera noise reduction, lens profile corrections, etc, AWB is imposed on the material after it comes off the sensor but before it is encoded internally as XAVC. 

By contrast the definition of true RAW is Bayer-format mosaic data read straight off the sensor and recorded essentially "as is" in ProRes RAW format. Therefore when recording ProRes RAW you don't have in-camera noise reduction, lens profile corrections, active steadyshot stabilization, or (with some Sony cameras) lens breathing compensation.

The advantage of ProRes RAW is the ambient white balance changes can be corrected in post without any side effects. The ability to correct is extensive --  you can set manual WB to 3000K then shoot in ambient conditions of 8000K, and it can be perfectly corrected. The downside is you have to correct it, apparently even if using AWB.

At least with ProRes RAW recorded on Ninja V from the Sony A7SIII, FX3, FX6, etc, you can do true WB adjustment in post. With the Atomos Shogun 7 you can't do that because Atomos never updated the firmware to permit that. 

Thank you for this.  What you say makes sense.  Therefore I am assuming that the reason I do not notice the color shift so drastically on the XAVC-S file is in part to processing and the application of stockless AWB, where as in the RAW file, it sees a change in temperature and just changes then and there.   

It is a little tricky then when transitioning from interior light to external lighting in the same shot.  I guess I will have to split the clip and adjust temperature accordingly on both parts

Thanks again.

Chris1603 wrote:

.. I am assuming that the reason I do not notice the color shift so drastically on the XAVC-S file is in part to processing and the application of stockless AWB, where as in the RAW file, it sees a change in temperature and just changes then and there...

In ProRes RAW there is no AWB. If the ambient light color temp changes (e.g, 7000K to 4000K), the recorded color balance of the RGGB mosaic image data changes in the ProRes RAW data stream. Technically there is no RGB color balance in Bayer-format RAW data since that is before RGB or chroma sampling exists in the processing stream. However the recorded RAW data if demosaiced and converted from to Rec.709 will show the ambient color temp, without any AWB compensation.

For XAVC-S (or any other non-RAW codec), AWB is applied continuously to the material before it is encoded. ProRes RAW cannot have corrections applied as it would alter the RAW video. It is theoretically possible to record Sony camera AWB metadata as an external metadata stream, which could be applied during NLE playback of ProRes RAW. However that would require a new metadata standard that would require coordination between Apple, Atomos and each different NLE maker.

Sony would have to devise a method of sending that, how to encode it in the RAW datastream, Atomos would have to devise a plan for encoding that,  The AWB continuous metadata would have to be stored somewhere -- in a sidecar file, in a hidden file, etc. -- on both Atomos and the downloaded files. Each NLE manufacturer supporting ProRes RAW would have to support that.

A similar situation exists for a fixed custom WB setting, except that is a single value -- not a continuous stream of varying AWB corrections. Handling a single WB value is much easier, so there is already a slot in the metadata to place that. It is easy to maintain that from camera to Atomos to NLE. It's easier for the NLE to decode and apply that one fixed setting. 

The bottom line is there are many things that don't work in ProRes RAW, and AWB is just one of them. In return ProRes RAW gives you the equivalent of 12-bit 4:4:4 recording, but in most cases I can't tell the difference between that and 10-bit 4:2:2 XAVC-I or XAVC-S.