Raw Isn’t Magic. With the right tools Log does it too.

Raw can be a brilliant tool, I use it a lot. High quality raw is my preferred way of shooting. But it isn’t magic, it’s just a different type of recording codec.
All too often – and I’m as guilty as anyone – people talk about raw as “raw sensor data” a term that implies that raw really is something very different to a normal recording. In reality it’s really not that different. When shooting raw all that happens is that the video frames from the sensor are recorded before they are converted to a colour image. A raw frame is still a picture, it’s just that it’s a bitmap image made up of brightness values, each pixel represented by a single brightness code value rather than a colour image where each location in the image is represented by 3 values one for each of Red, Green and Blue or Luma, Cb and Cr.

As that raw frame is still nothing more than a normal bitmap all the cameras settings such as white balance, ISO etc are in fact baked in to the recording. Each pixel only has one single value and that value will have been determined by the way the camera is setup. Nothing you do in post production can change what was actually recorded. Most CMOS sensors are daylight balanced, so unless the camera adjusts the white balance prior to recording – which is what Sony normally do – your raw recording will be daylight balanced.

Modern cameras when shooting log or raw also record metadata that describes how the camera was set when the image was captured. 

So the recorded raw file already has a particular white balance and ISO. I know lots of people will be disappointed to hear this or simply refuse to believe this but that’s the truth about a raw bitmap image with a single code value for each pixel and that value is determined by the camera settings.

This can be adjusted later in post production, but the adjustment range is not unlimited and it is not the same as making an adjustment in the camera. Plus there can be consequences to the image quality if you make large adjustments. 

Log can be also adjusted extensively in post too. For decades feature films shot on film were scanned using 10 bit Cineon log (which is the log gamma curve S-Log3 is based on) and 10 bit log used for post production until 12 bit and then 16 bit linear intermediates came along like OpenEXR. So this should tell you that actually log can be graded very well and very extensively.

But then many people will tell you that you can’t grade log as well as raw. Often they will give photographers as an example where there is a huge difference between what you can do with a raw photo and a normal image. But we also have to remember this is typically comparing what you can do with a highly compressed 8 bit jpeg file and an often uncompressed 12 or 14 bit raw file. It’s not a fair comparison, of course you would expect the 14 bit file to be better.

The other argument often given is that it’s very hard to change the white balance of log in post, it doesn’t look right or it falls apart. Often these issues are nothing to do with the log recording but more to do with the tools being used.

When you work with raw in your editing or grading software you will almost always be using a dedicated raw tool or raw plugin designed for the flavour of raw you are using. As a result everything you do to the file is optimised for the exact flavour of raw you are dealing with. It shouldn’t come as a surprise to find that to get the best from log you should be using tools specifically designed for the type of log you are using. In the example below you can see how Sony’s Catalyst Browse can perfectly correctly change the white balance and exposure of S-log material with simple sliders just as effectively as most raw formats.
Screenshot-2020-11-27-at-17.14.07 Raw Isn't Magic. With the right tools Log does it too.
On the left is the original S-Log3 clip with the wrong white balance (3200K) and on the left is the corrected image. The only corrections made are via the Temperature slider and exposure slider.
Applying the normal linear or power law (709 is power law) corrections found in most edit software to Log won’t have the desired effect and basic edit software rarely has proper log controls. You need to use a proper grading package like Resolve and it’s dedicated log controls. Better still some form of colour managed workflow like ACES where your specific type of log is precisely converted on the fly to a special digital intermediate and the corrections are made to the intermediate file. There is no transcoding, you just tell ACES what the footage was was shot on and magic happens under the hood. Once you have done that you can change the white balance or ISO of log material in exactly the same way as raw. There is very, very little difference.
Screenshot-2020-11-27-at-17.29.27 Raw Isn't Magic. With the right tools Log does it too.
The same S-Log3 clip as in the above example, this time in DaVinci Resolve using ACES. The only corrections being made are via the Temp slider for the white balance change and the Log-Offset wheel which in ACES provides a precise exposure adjustment.
When people say you can’t push log, more often than not it isn’t a matter of can’t, it’s a case of can – but you need to use the right tools.
After-correction-450x253 Raw Isn't Magic. With the right tools Log does it too.
This is what log shot with completely the wrong white balance and slightly over exposed looks like after using nothing but the WB and ISO sliders in Catalyst Browse. I don’t believe raw would have looked any different.
Less compression or a greater bit depth are where the biggest differences between a log or raw recording come from, not so much from whether the data is log or raw.  Don’t forget raw is often recorded using log, which kind of makes the “you can’t grade log” argument a bit daft.
Camera manufactures and raw recorder manufacturers are perfectly happy to allow everyone to believe raw is magic and worse still, let people believe that ANY type of raw must be better than all other types of recordings. Read though any camera forum and you will see plenty of examples of “it’s raw so it must be better” or “I need raw because log isn’t as good” without any comprehension of what raw is and how in reality it’s the way the raw is compressed and the bit depth that really matters.

If we take ProRes Raw as an example: For a 4K 24/25fps file the bit rate is around 900Mb/s. For a conventional ProRes HQ file the bit rate is around 800Mb/s. So the file size difference between the two is not at all big.
But the ProRes Raw file only has to store around 1/3 as many data points as the component ProResHQ file. As a result, even though the ProRes Raw file often has a higher bit depth, which in itself usually means better a better quality recording, it is also much, much less compressed and as a result will have fewer artefacts. 

It’s the reduced compression and deeper bit depth possible with raw that can lead to higher quality recordings and as a result may bring some grading advantages compared to a normal ProRes or other compressed file. The best bit is there is no significant file size penalty. So you have the same amount of data, but you data should be of higher quality. So given that you won’t need more storage, which should you use? The higher bit depth less compressed file or the more compressed file?

But, not all raw files are the same. Some cameras feature highly compressed 10 bit raw, which frankly won’t be any better than most other 10 bit recordings as you are having to do all the complex math to create a colour image starting with just 10 bit. Most cameras do this internally at at least 12 bit. I believe raw needs to be at least 12 bit to be worth having.

If you could record uncompressed 12 bit RGB or 12 bit component log from these cameras that would likely be just as good and just as flexible as any raw recordings. But the files would be huge. It’s not that raw is magic, it’s just that raw is generally much less compressed and  depending on the camera may also have a greater bit depth. That’s where the benefits come from.

8 thoughts on “Raw Isn’t Magic. With the right tools Log does it too.”

  1. Great article!

    Is one other thing perhaps worth mentioning differences in debayer algorithms and how this may have an effect? And the potential for material to be “re-debayered” in the future should an improved algorithm cone about?

    1. Yes, this is possible in theory. But in practice this is rare and any improvements are generally very small.

      But – codec decoders also improve and edit techniques improve, so log recordings and what you can do with them can also improve.

  2. Thanks Alister for the clear explanations, it’s so great you freely share your knowledge with everyone.
    I posted a question about this on the FB FX9 user group and your article now has really helped clarify the information to process.
    The bigger question i seem to have now is to jump from FCPX to Da Vinci given the colour grading advantages in it – but i guess i could first try to import and slog3 edit from FCPX into Resolve then grade this for now.
    Potentially using ProResRAW down the track keeps me with FCPX.

    1. You can use FCPX to convert the ProResRaw to S-Log3 ProRes444 which is a 12 bit codec and then grade that in Resolve. It’s not the best way to use raw but it works and looks good.

      1. Thanks Alister, great to know!
        I plan to grade my current project which was shot in slog3 in Da Vinci after I hopefully finish the shoot early next year.

    1. An 8 bit recording just isn’t going to give you the same quality as 10 bit. It doesn’t mean you can’t adjust 8 bit log but it’s going to degrade much faster than a better quality recording.

  3. Great article.
    Especially liked the bit about correcting log in NLEs. Im still using Premiere (because of AE workflow) and correcting log is just so different when you use lumetri vs a tool which really knows the camera sensor. Take for instance the new Cinematch from ficomvert which can be used for exposure and WB adjusting footage but has the advantage of knowing a whole bunch of cameras. With that tool I find that you can push 10 bit log footage quite a lot.

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