S-log, cheap 'n easy?

[Jim Tittle]

Can I shoot S-log video, record it with a Ki-pro mini, and apply a LUT in post? I'd like to be able to shoot a "digital negative", but I won't have access to Sony's new digital recorder. I also won't have access to a post facility with a professional colorist.

[James Houk]

No, that's not possible. The S-Log signal feeds out of the Dual HD-SDI ports and is 4:4:4 RGB. The Ki Pro, Nanoflash, and similar devices can only record 4:2:2, and should appropriately be attached to the single SDI spigot on the top right rear of the camera. That port is designed to be used for onset monitoring during S-Log recording, so the LUT can either be displayed or turned off, but the recorded result is baked in.

To use S-Log you would need to purchase the firmware upgrade, rent or buy an appropriate recorder, and then, (after any SxS offline editing) move to a suitable online edit suite.

I suspect if you only occasionally have use for S-Log that renting a recorder may be the most economical option.

[Jim Tittle]

I understand--with S-log, there's so much data that it takes dual SDI and a special recorder to handle it. (Under most circumstances, I don't think my clients will want to take that route. Nice to know it's there, though.)

I'm curious: what would constitute a "suitable online edit suite"? What software do you use to apply the LUTs?

And, back to the more primitive world that I live in: even without the S-log feature, a Pro Res file recorded from the SDI output of the camera is going to allow quite a bit of room for color correction, right?

[Jim Tittle]

One more thing: I'm a little confused about this term, "Baked In". Suddenly, I see it everywhere.
Can anyone offer an exact, technical definition of what this means? "Adjustments applied, file size reduced"? Right now, every time I hear that term, "Baked", I sneeze.

[James Houk]

Camera sensors collect a lot more data than is generally possible (or sometimes even desirable) to record. In camcorder mode white balance, knee, gamma curves, gain - these are all internal adjustments to the data after it has been collected by the sensor. For any camera output the data has to be conformed to the specifications of that signal type. For any internal recording media the data has to be compressed to that codec.

Basically, you tell the camera which sensor data you wish to retain, and which to discard. What's recorded to the SxS cards is only a fraction of what the camera sensor saw.

As Alister Chapman has previously pointed out, S Log is not a true uncompressed copy of the camera sensor data - I believe he said there is some highlight compression applied (among other things), but it's the closest this camera can get to it.

So... for your SxS or Nanoflash, you can consider what it records to be "baked" because there is no going back and unapplying the gamma or LUT once it's been recorded to that compressed media.


I own an EX1 which uses XDCAM EX. The footage has an impressive amount of lattitude for it's size. I've also recorded ProRes footage from the 10bit HD-SDI, and that definitely gives you even more room to make adjustments in post. Just not as much as S Log would.

[Dave Sperling]

Hi Jim,
The way I think of it, with the HyperGamma settings you can essentially compress about two stops of (overexposed) highlights down into your recordable range. (that is where the hypergamma curves bring 400%+ of video down to 100% or 109% video level.) This can then be color-corrected to massage the data a little more, or you may find you like the look. Remember, though, that anything recorded at above that range is completely gone. High quality pro-res should be fine for this, and presumably SR would be even better for basic color correction.
With S-Log you're getting the full range of the chip, which I interpret to mean up to around 800% video (or one extra f/stop of highlight detail to work with), crushed down into your recording range - using a logarithmic system so that you still have excellent color-correctability in the blacks and mid-tones where it really counts. Obviously, because S-Log gives you a larger range of recorded exposure to work from, you have more room for color correction.
But with S-Log you will absolutely have to do a post-color-correct on the footage, whereas with the Hypergammas you may like the look (or not need to do as comprehensive a color correct.)
If you don't have access to a professional colorist, you will need to do a lot of learning/testing/practicing to get yourself up to speed if you want to use S-Log.
I'm sure that once the F3 camera and dual link option become available and popular, especially since Sony seems to be starting to open up the SR codec at the software level (based on what Peter Crithary said in his Rule presentation, available elsewhere in this forum), we will start to see even more recording options become available.
'Baked In' -- to me that just means that a LUT has been applied to the image, and the image is recorded post-LUT, so there's no way to remove the LUT and get the image recorded on the SxS cards back to the way the S-Log data looked. That's why the image on the SxS cards doesn't look like the S-log data.

Feel free to correct me if I'm not getting it straight...

[Jim Tittle]

Thanks for the information.

As a guy who started out shooting large-format Ektachrome, all of this image control is and exciting prospect.

[Doug Jensen]

Originally Posted by Dave Sperling

Feel free to correct me if I'm not getting it straight...

Dave, I think you have summed it up perfectly.

[Alister Chapman]

The big difference between 4:4:4 and 4:2:2 is that 4:4:4 is RGB so you have the full S-Log data from each sensor so you can adjust the individual colours to get the exact tonal response that you want, so in effect you can colour balance in post. With 4:2:2 YUV your colour balance is pretty much baked in when you shoot. You can correct and adjust it but there just isn't as much lee-way as with RGB.

[Nate Weaver]

Originally Posted by Jim Tittle

I understand--with S-log, there's so much data that it takes dual SDI and a special recorder to handle it.

I wouldn't describe it like that. While Sony has bundled S-Log and 4:4:4 together (as of now), they are useful independently. The only dependency I can think of that hasn't been discussed is that S-Log isn't that useful if it's recorded to an 8-bit codec. Since S-Log needs to be manipulated later, you need those 10 bits to keep the image from posterizing as you "stretch it back out" with contrast later.

Originally Posted by Jim Tittle

And, back to the more primitive world that I live in: even without the S-log feature, a Pro Res file recorded from the SDI output of the camera is going to allow quite a bit of room for color correction, right?

It's going to allow more, yes, but understand a good portion of that magic is in recording to a 10-bit format as opposed to an 8-bit format. This means KiMini as opposed to Nanoflash, at the moment.

[Alister Chapman]

S-Log at 8 bit will look terrible with lots of banding. As you have to convert the log recording to near linear for a sensible looking image there will be a lot of pulling and pushing of the image and you must have 10 bit for it to look decent.

[Jim Tittle]

So, with a standard F3, I'll be able to record a low contrast scene -- broad tonal scale-- with my Ki Pro Mini through the SDI output, at 10 bits. Apple Final Cut Studio can handle 10-bit?

The key to all of this is the 10-bit SDI output? Right now, if I record a flat, low con, scene through the SDI output of my HPX-500, it would fall apart if I try to correct it much, correct?

As a matter of course, I usually use a "low-contrast" style with my Canon 5D. But I can't seem to correct it much in post, because the video's already been through the meat grinder.

[David Heath]

Originally Posted by Jim Tittle

The key to all of this is the 10-bit SDI output?

Yes - together with a low noise camera - and that is the bit that's all too often forgotten.

There's no point in 10 bit recording for most cameras because even if the bit depth will permit pushing and pulling without banding, the noise will stop it instead for other reasons. The indications seem to be that the F3 will have a low enough noise level to make 10 bit worthwhile.

[Jim Tittle]

I understand. Thanks for clarifying this.

[Nate Weaver]

Originally Posted by David Heath

There's no point in 10 bit recording for most cameras because even if the bit depth will permit pushing and pulling without banding, the noise will stop it instead for other reasons.

As a part-time colorist, I disagree. Colorists need images not to posterize as we manipulate, no matter where the noise floor/level is from the camera. And it can't be fixed by transcoding 8-bit to 10-bit. No matter how flawed the original signal is, capturing it in 10-bits helps later if you color.