The Pro’s and Con’s of 12 bit linear raw or recording raw to S-Log.


This came up in the comments today and it’s something that I get asked about quite a lot.

Sony’s high end cameras, designed for raw – F5, F55, F65 all use 16 bit linear data. This linear data contains an impressively large amount of picture information across the entire range from the darkest shadows to the brightest highlights. This huge amount of data gives footage that can be pushed and pulled in post all over the place. 16 bit raw gives you 65,536 discreet values.

The FS7 and FS5 use 12 bit linear raw. 12 bit data gives you 4096 discreet values, 1/15th of the values, a small fraction of what 16 bit has. This presents a problem as to record 14 stops with linear data you need more than 12 bits.

Not Enough Code Values.

There just aren’t enough code values with only 12 bits (which is why no one else does it). So Sony do some clever math to make it workable. This reduces the amount of tonal steps in in the shadows.  On it’s own this isn’t a huge problem, just make sure you expose brightly to avoid trying to pull to much info out of the shadows and definitely don’t use it for low light. On high key scenes 12 bit raw is very nice indeed, this is where it excels. On low key scenes it can appear very grainy, noisy and shadows often look coarse and lack smooth textures. Expose nice and bright and you will get great highly gradable footage. Expose dark and you will have big problems.

Transcoding can add to the problems.

Where you really can run into problems is if you take 12 bit raw (with it’s reduced shadow data) and convert that to 10 bit log (which has reduced highlight data relative to the scene you are shooting).

What you end up with is 10 bit log with reduced shadow data compared to a straight 10 bit log recording. If you compare the direct 10 bit S-log from an FS7 (or F5/F55) to 10 bit S-log derived from 12 bit raw from an FS5, the FS7 internal 10 bit log picture will have a little more shadow information while the highlights from both will be similar. So the direct internal 10 bit log recording from an FS7 will typically be a little better in the shadows than any log created from the 12  bit raw and there will little, if any, highlight benefit.  It’s a little different for the FS5 as in UHD this is limited to 8 bit, so the raw, converted to log from the FS5 will have better highlight data, but still be a touch weak in the darkest shadow areas.  Overall  10bit log derived from 12 bit linear will be better than 8 bit log, but not better than 10 bit log.

If 4K S-Log is really important to you – get an FS7, F5 or F55.

So I’d much rather have an FS7 (F5 or F55) if I want to shoot UHD or 4K S-log. That’s what these cameras are designed for. But, if you only have an FS5, the raw to log workflow will outperform the limited 8 bit UHD log, so it is still definitely beneficial for FS5 owners to shoot raw and convert it to 10 bit S-Log with an external recorder. But better still record raw, then you really will have a better image.

Raw with the FS7.

300x250_xdcam_150dpi The Pro's and Con's of 12 bit linear raw or recording raw to S-Log.

On the FS7 the benefits of recording 12 bit raw over 10 bit S-Log are less clear. For bright, well exposed scenes the 12 bit raw will  have a definite  edge. For low light or under exposed scenes there is no benefit to shooting 12 bit raw you will get nothing extra.

On the FS7 it is not a good idea to take the 12 bit raw output and record it as 10 bit S-Log on an external recorder. While you may have a less compressed codec, you will be compromising the shadows compared to the cameras own internally generated 10 bit log recordings.  In most cases you would be better off simply taking the HDMI output and recording that as it avoids the 12 bit linear shadow bottleneck.

Again though – exposing nice and bright is the key to a good result. Get the data up into the brighter parts of the recording and the raw can be fantastic.

Internal and external log brightness shifts.

When you record S-Log internally on the Sony cameras the recordings use full range data levels to maximise the codec performance. You can use data range (which exceeds the normal video range) as it is assumed the data will be graded and as part of this process restored to video range data for viewing. However when recording on an external recorder the recordings sometimes use full video range rather than data range or if it’s data range don’t have the right metadata. This shouldn’t be a huge problem if the grading software behaves itself and treats each type of content correctly, shifting each to one unified range, but sadly this is rarely the case (especially with Adobe). So not only do the internal and externally recorded images come out with different brightness and contrast, but also LUT’s designed for one don’t work the same with the other. It’s a bit of a minefield to be honest and one of the reason why I prefer to always grade with dedicated grading software like resolve which handles the levels conversions properly (most of the time at least).

460x150_xdcam_150dpi The Pro's and Con's of 12 bit linear raw or recording raw to S-Log.

10 thoughts on “The Pro’s and Con’s of 12 bit linear raw or recording raw to S-Log.”

  1. Is this correct:

    If using an FS5 to a raw recorder, it is better to send:
    – Raw out to ProRes Raw recording
    – Raw out to ProRes but do not use a LOG picture profile in the camera

    Following the second option, this would then not allow a user to record 10-bit UHD LOG internally (back-up) while also recording external RAW to ProRes 422 (because the output would be in LOG).

    1. If outputting raw you absolutely MUST use profile 7. It must be set to S-Gamut2 and S-Log2. Any other settings will result in extra noise or odd colours. Then if you want the full benefits of the raw out then you should record raw, converting to log in the recorder limits how much you can grade the footage and if it’s not well exposed result in noisy shadow areas that are hard to correct.

  2. Trying to understand here.

    I have an FS5ii with Atomos Shogun 7 and I want to understand what recording ProsResRAW will give me.

    Is it 12bit linear when recorded as ProResRAW?

    Re exposure, are we saying that even for low key moody scenes we should expose high key and then bring down in post?

    I was hoping to shoot my first horror feature on the FS5ii + Shogun 7 setup, mainly as it’s what I have lol but if the moody/low key look is junk on this setup I may need to look at something else…

    1. It is 12 bit linear, a very inefficient way to record a large dynamic range and as a result suffers from compression and noise artefacts in the lower range. Expose well and it looks great, underexpose and it looks poor (but then any camera underexposed won’t look great). Just add more light or use a faster lens so you can expose a bit brighter. You can have exactly the same look/contrast/shadows etc by increasing the light equally across all aspects of the scene or by using a faster lens and exposing brighter and then bring it down in post by the same corresponding amount.

  3. Is there any difference recording prores through the SDI or the HDMI port on the FS5? The prores from the SDI seems to be converted from the 12 bit raw data. Then how is it about the prores from the HDMI port? Thank you so much!

    1. There is no difference in the conventional (non raw) signal out of the SDI or HDMI ports. Neither are “converted from the raw”. They are both 8 bit in UHD/4K and come from the cameras normal internal processing.

  4. Hello Alister,

    thanks for this article and also your great videos on YT.
    I have a question concerning the fs700 from sony.
    What are the best Settings concerning Log, picture profile and ISO if you want to record prores raw with an Atomos Recorder? All the best, Eric

    1. You must use SGamut and S-Log2 if you want the full dynamic range, ideally PP7 and 0dB gain.

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