Why is the white balance limited to 3 presets when using S-Log2, S-Log3 or raw?

This seems to be a source of frustration for many people shooting  raw or using S-Log2 or S-Log3 on a Sony camera. When shooting log and raw you should also be using a matching S-Gamut colour gamut if you want to get the best from the camera and this ties you into one of 3 preset white balances.

With a PXW-FS7, PMW-F5 or F55 it is possible to use custom mode to select a different colour space to mix with S-Log2 or S-Log3 and then have a variable white balance. With the Alpha cameras, PXW cameras such as the FS5 you can choose any Gamut you want in the picture profiles, but I don’t recommend this. For a start, if you don’t use one of the S-Gamuts you will be limited to Rec-709 Gamut, so you won’t be recording  the cameras full colour range. Also in custom mode there are some other things like noise reduction that you really don’t want when shooting S-log2/3 (it can cause banding).

So why is the S-Gamut white balance fixed to the 3 presets for daylight, fluorescent and tungsten? The main reason is to ensure you get the cameras full dynamic range in each colour. White balance is a gain function, it adjusts the gain of the red, green and blue channels so that white objects appear white under differing light sources. So if the light source lacks blue light – making the pictures look excessively warm – you add extra gain to the blue channel to compensate.

But the problem with this is that gain affects dynamic range. When shooting log (or raw) the camera needs to operate the sensor at the optimum gain level to squeeze the highest possible dynamic range from the it. Changing the gain in just one colour channel to shift the white balance could result in a reduction of dynamic range in the channel. This could manifest itself as colours in one channel that clip sooner than the others. This can be really hard to deal with in post production and can show up as things like bright clouds with a colour cast that isn’t in the rest of the picture.

Another potential issue is that because of the way silicon sensors work the blue channel is almost always noisier than the red and green. So you want to keep the gain in the blue channel as low as possible to prevent the pictures getting too noisy. This is particularly important when shooting log as you won’t see your end result until after the images have been graded. So manually shifting the gain of the blue channel in camera to correct the white balance could lead to footage that ends up noisier than you would expect.

So – Sony chose to fix the white balance to 3 carefully tuned presets designed to avoid this situation and maximise the dynamic range. After all, when shooting log or raw it is expected that the footage will be graded anyway, so the white balance will normally be adjusted as part of the post production process.

There are some people that advocate adjusting the FS5’s white balance via the picture profile settings, personally I don’t recommend this or feel that it’s necessary. But yes, you can do this, but just keep a very close eye on your highlights and if you can use monitor with RGB parade to make sure you have equal recording levels for your whites without one colour channel clipping ahead of the others. Also apply a LUT in the monitor that is close to your desired output so that you can keep an eye on the noise levels.

In summary – the white balance is preset to ensure you don’t encounter problems later on. You should be able to fully adjust and fine tune your white balance in post production to a far greater degree than is possible in camera anyway, so don’t worry if the WB is a touch off when shooting.

The only exception to this is the new Sony Venice. Venice has enough dynamic range and enough internal processing power to allow you to make a wide range of white balance adjustments in camera. Hopefully we will see some of this flexibility trickle down to the next generations of lower cost Sony digital cinema cameras.

460x150_xdcam_150dpi Why is the white balance limited to 3 presets when using S-Log2, S-Log3 or raw?

6 thoughts on “Why is the white balance limited to 3 presets when using S-Log2, S-Log3 or raw?”

  1. Hi Alister,

    Very interesting post!
    I’m a bit confused though …
    As far as I understand every time we shoot (white balance) in a color temperature other than the sensor’s native color we will invariably reduce the dynamic range of some color channels, whether it’s manual or preset change. Therefore I don’t find any theoretical advantage in using preset color temperatures. Am I wrong?



  2. G’day Alistair, Thanks for the helpful info! There are some things on my Sony HXR-NX80 that I don’t quite understand, one of those is the S-Gamut3 WB presets, it has 3200K, 4300K & 5500K. I have been using it in S-Log2 set to S-Gamut3/5500K because the other two add a lot of blue to the image, I can’t seem to work out what situation they would be useful for when they add so much blue, I haven’t adjusted any of the other settings in PP7 other than the preset WB number. Are you able to tell me what it is I’m not understanding about these S-Gamut3 WB presets? and is it okay for me to be using 5500K for all my shots or is there something else I should be adjusting to get a better image?


    1. Normally you would use 3200K when shooting under tungsten or incandescent lights, 4300K under some types of florescent lights. But with LED and florescent lights replacing incandescent lights the need for 3200K is less than it used to be.

    2. Hello.
      Is that apply to other Sony cameras ? Lets say the a7sii / a7iii ?
      Thank you for all the infos.

  3. Hello Mr. Chapman,
    i know, this is a very old post. But maybe you can answer my question anyway.
    I love seeing your tutorials and webinars. I find them allways very helpful and im thankfull you share your knowledge with us.
    I work as a cameraman a couple of years now for a german TV Station. And i used to Film only within the Rec. 709 Standard.
    I have absolutely no experience in filming with slog3 but im very interested in. And now my next projekt should be filmed with the FX9 in s-log 3.
    I studied a lot of Tutorials, especially your fx9 and fs7 Tutorials on YouTube about Slog.
    As i said, I use the Sony FX 9 Camera and i did a few test shootings.
    But i‘m unsecure about the white Balance during shooting in S-log 3.
    May i Balance my white manually on every new Location as i do normaly? Or is this in slog Not nessasary or a bad thing?
    Do i have to use only the 3 WB Presets instead of white balancing the Camera manually?
    About the right white Balance while shooting in S-log, i can not find clear informations which answers my question realy clear.
    Maybe you can help me and answer my question.
    Thank you and have a nice Weekend.

    1. The 3 presets was a limitation of the previous generation of cameras that we no longer have. You should white balance exactly as you would with any other gamma curve. S-Log3 will give you more room for adjustment in post production, but getting the WB right in camera can save a lot of work later.

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