F55: F5/F7/F55 CineEI LUT primer, quick quide & history

Guys,

As a new FS7 adept, I just started my adventure with S-log shooting, so this thread has been of great value to me. One thing I still don't quite "feel" yet though: am I right saying that we record S-log 2 or 3 to preserve as much DR as possible, so simply de-logging the picture (either in camera by baking-in a LUT, or in NLE - following Sam's "one click" philosophy - applying a LUT) is somewhat counter-productive? Of course I'm putting all "special cases/needs" aside, but generally - shouldn't we grade the "logarithmic domain" picture, using logarithmic tools - if we're after preserving that wide DR we used S-log for in the first place? I don't know how to use Resolve (yet; I will be learning), but only this NLE seems to offer "logarithmic color wheels" - or am I wrong here, and using regular color correction tools in Vegas Pro or Premiere is just as good?

Or maybe my greatest misconception stems from the fact the applying a LUT (the "one-click NLE strategy"...) doesn't necessarily "de-log" the picture (i.e. puts it back into the 5-7 stops confinement)?

Lots of newbie questions, but please be easy on me :)

Piotr
 
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Think of shooting log as a 14-stop pint glass which you fill with sexy beer footage.

Think of REC709 colour space as a 7-stop half pint glass.

This process is going to allow you to (within reason) which bits of the footage beer you want to fill your half pint glass with


In Resolve I put the log to REC709 transform LUT on a the final node so that all the adjustments are happening to the log footage before I change the colour space. You can apply that same philosophy to Lumetri in Premiere or similar elsewhere.


If you're baking in a LUT while shooting you are (more often than not) going to a REC709 colour space and so do not have that choice of what goes into the half pint glass other than controlling what is in front of the camera.


Just to explain something else though. You can grade log footage directly without using any technical conversion LUTs but log footage is SUPPOSED to be converted to REC709 via a technical LUT and to not do this risks all manner of problems. To quote Chris Rock 'you can drive with you feet if you want to, but that don't make it a good idea'.
 
Ben Scott said:
Just to explain something else though. You can grade log footage directly without using any technical conversion LUTs but log footage is SUPPOSED to be converted to REC709 via a technical LUT and to not do this risks all manner of problems. To quote Chris Rock 'you can drive with you feet if you want to, but that don't make it a good idea'.
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Am I right understanding that the above statement is only true because of the final product being watched on 709 color space monitors/TVs, and should I somehow get able to watch it on a 2020-color space device it isn't true anymore?
 
Correct. In which case swap out that end transform LUT to a REC2020 one and all your gradings should be the same.

Whereas if you had the LUT at the start of the chain you'd have the change everything.
 
^ And this is great advice for any "future-proofing" (if that phrase can even be used is a whole other topic) of projects that might have the legs to eventually see the 2020 color space output.
 
Ben Scott said:
In Resolve I put the log to REC709 transform LUT on a the final node so that all the adjustments are happening to the log footage before I change the colour space. You can apply that same philosophy to Lumetri in Premiere or similar elsewhere.
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There is a caveat to what you just said - or Vegas Pro cannot grade S-log footage without de-logging it...

I just graded the same Slog3 clip in 2 ways in Vegas Pro:

1. Applied a REC709 LUT first, and did some tweaks in VP; I got a nice "normal"- looking picture
2. Did everything using VP's cc tools so that the image adopted "normal" contrast, levels and saturation first, and then applied a REC709 LUT.

Unfortunately - as I feared - the way number 2 gave me an "overdone" picture (as if I applied the REC709 LUT *twice*).

So again: do I need Resolve (or similar ) NLE with "log" grading tools for your workflow to work, or am I still missing sth?
 
Oh, if there's a difficult or stupid way to do something I'm sure Sony will find it.

You might be better off 'round tripping' your vegas edit to resolve and grading and then relinking your vegas sequence to the new resolve graded and exported clips.
 
I think the use of Resolve should be required by law when shooting S-LOG. The color correction controls (I cannot call them grading tools) in any NLE fall woefully short when compared to the amazing power of Resolve. Anyone who is concerned enough about image quality that they are going to shoot LOG shouldn't hesitate to also make the effort to process it in post the best way possible. And that means Resolve, Baselight, or some other dedicated grading program. And since Resolve is free, there is really no excuse not to.
 
If one is going to use Vegas for S-Log, they really ought to use the built in supported workflow for it. It's really good, just check the help files or google to look up the workflow. With it you can forget de-logging LUTs all together.
 
Ben Scott said:
Oh, if there's a difficult or stupid way to do something I'm sure Sony will find it.

You might be better off 'round tripping' your vegas edit to resolve and grading and then relinking your vegas sequence to the new resolve graded and exported clips.
Click to expand...

Oh, let's not dismiss it so lightly - there must be a very simple thing we're both missing; me - because I'm new to working with log gammas/color spaces, and you - because you've been working with them using the right tools for so long your workflow became a routine; perhaps too much so for you to answer my (hopefully legit) questions...

Doug Jensen said:
I think the use of Resolve should be required by law when shooting S-LOG. The color correction controls (I cannot call them grading tools) in any NLE fall woefully short when compared to the amazing power of Resolve. Anyone who is concerned enough about image quality that they are going to shoot LOG shouldn't hesitate to also make the effort to process it in post the best way possible. And that means Resolve, Baselight, or some other dedicated grading program. And since Resolve is free, there is really no excuse not to.
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Totally agree, Doug - and as mentioned above, am going to master Resolve :) But in the meantime: the color wheels in Resolve can be used in "log" mode; would you care to explain what it really means? Of course I have my idea on this, but - to use them correctly - full understanding is necessary. So please flatten my learning curve, and shed some light on it - will you?

starcentral said:
If one is going to use Vegas for S-Log, they really ought to use the built in supported workflow for it. It's really good, just check the help files or google to look up the workflow. With it you can forget de-logging LUTs all together.
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Which help file do you mean - the one for Resolve or Vegas?
 
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Gents - let me add that I'm in a somewhat special situation here compared to most of you, because:

1. I'm not a pro anymore, due to a serious neck spine condition - so I'm going to "deliver" for myself, and do not have to strictly follow REC709 most displays out there are using. Let me tell you that I'm using a Samsung "Quantum Dot" KUHD TV, which not only offers excellent wide color gamut, HDR (in what Samsung calls HDR1000), but also enables full 10 bit path from my NLE, through my graphics card to the screen - REC709 would severely limit its potential. So even if I logged with some LUT, it certainly wouldn't be any standard Sony S-log2/3->REC709 one. Of course I realize this is still far inferior to the reference professional monitor - but frankly, even if I had that kind of money, it wouldn't be wise to buy one in my situation...

2. As mentioned earlier, being new to log gammas I'm not confined by routines and open to new ways and your suggestions/help/advise!

3. Last but not least: I don't dismiss anyone's advise, including Alister's or Doug's ;-)

So, being enthusiastic about my new FS7 camera and editing suite (well - at least the hardware), I'm looking forward to a great fun and excellent results :)

Piotr
 
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moldcad said:
So please flatten my learning curve, and shed some light on it - will you?
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No I will not be spending my time on that. You have stated quite clearly on another forum that you have no interest in what I have to say so I will leave it to others to help you if they choose to. You already burnt your bridges with me. But I must say your constant begging for people to help you is getting tiresome. Why don't you go out and actually use the camera, experiment with the settings, compare A vs. B when you're not sure about something, and then ask for feedback after you post your work. There is no substitute for actually getting out and using the camera, buying one is just the first step.
 
You know what, Doug? I had no idea that a grown and accomplished man can bear aversion to somebody for so long - I'm not like this. Even if I have a controversy with someone, as soon as he/she doesn't treat me with hostility any longer I promptly forget about all past confrontations and move along.

You're clearly not like that, pity because I appreciate your knowledge and experience and never said "on another forum that I have no interest in what you have to say". If you understood me like this, it's your problem - but to put effort to bash me in two separate threads like this?

What makes you think I "never go out and actually use the camera, experiment with the settings, compare A vs. B" before I ask a question on a forum? Your hostility towards me seems to handicap your understanding of my posts. Why not simply ignore them, Doug - rather than take time and effort to post answers like this?

Stay cool,

Piotr
 
Dennis,

After I gave the ACES workflow in Vegas Pro - as opposed to straightforward Resolve workflow - a second thought, here are some of my thoughts:

1. Vegas Pro has always been a really great NLE for me; intuitive and complete. However, there are two main shortcomings:

a) working with 32-bit pixel precision (required by ACES, or for 10 bit material in general) can be a PITA, as SCS worked the GPU engine around CUDA as implemented in the first generation of nVidia cards (Fermi) - so it's painfully slow to playback the timeline or render on newer computers (even with faster CPU, but newer nVidia cards)

b) knowing how Resolve's Color Wheels preserve DR, and with Vegas not offering them, I'm afraid only basic Vegas tools like Color Curves or Gamma can do the same; am I to understand that with ACES, RRT and IDT, all other regular grading tools in Vegas also preserve DR and do not clip S-log video?

Anyway, even if the answer to point b) is positive - because Vegas Pro development seems to have stopped at v. 13 (nobody knows for sure what its future will be) - I think the only viable workflow is somehow marry Resolve with Vegas Pro (of course I'm mentioning VP only with those in mind who - like myself - are long-time users of this NLE and appreciate it for said completeness and efficiency).

So, for instance, one such workflow could be:

- do all grading in Resolve
- export EDL and import it to Vegas Pro
- finish the edit with all the things that VP is good at (like sound)
- render out to a format of choice

Considering the limitations of working in VP in 32-bit pixel mode, it would be ideal if turning it on for ACES compatibility should only be necessary at the very last stage: rendering out. Alas - from what I read in the PDF you linked to - ALL effects (e.g. crossfades etc.), NOT just grading tools, will only preserve S-log material DR in ACES mode - which means All editing in VP must be done with 32-bit pixel precision:(. Which means that my workflow proposal above needs lots of consideration and tweaks to it... Who knows - perhaps it will turn out that the only viable solution to incorporate VP's comprehensive tools that Resolve lacks would be to do the Vegas part of the workflow using proxies, which hopefully would allow less pathetic TL playback EVEN with 32-bit on?

Piotr
 
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moldcad said:
There is a caveat to what you just said - or Vegas Pro cannot grade S-log footage without de-logging it...

I just graded the same Slog3 clip in 2 ways in Vegas Pro:

1. Applied a REC709 LUT first, and did some tweaks in VP; I got a nice "normal"- looking picture
2. Did everything using VP's cc tools so that the image adopted "normal" contrast, levels and saturation first, and then applied a REC709 LUT.

Unfortunately - as I feared - the way number 2 gave me an "overdone" picture (as if I applied the REC709 LUT *twice*).

So again: do I need Resolve (or similar ) NLE with "log" grading tools for your workflow to work, or am I still missing sth?
Click to expand...


Hi Piotr,

it sounds like things have progressed from this post, but just to reply:

a LUT is designed to be applied to a particular, consistent colour space. In the case of ones provided by maufacturers or 3rd party LUT companies, they are generally designed for particular transfer function (typically flavours log log) and colour space (S-Gamut, S-Gamut3.cine, Arri Wide Gamut etc).

In the case of a Rec709 LUT, this will convert both the colour space / gamut element (eg from S-Gamut3.cine to Rec709 primaries and white point) and the transfer function / gamma (eg from S-Log3 to Rec709 gamma with a highlight rolloff / soft knee as in the case of Rec709(800%) ).

If you correct before applying the LUT, it is no longer the combination expected by the LUT and things will go awry; particularly so if you adjust the contrast. That is what you see in option 2.

Now there are two possible approaches. One is ACES, which converts everything to pure scene linear (each stop is a doubling of floating point values) and generally AP0 colourspace (ACES own primaries and white point, which cover the whole of the visual gamut, but consequently looks bizarre on a Rec709 or Rec2020 monitor and is so flat that it really needs floating point or deep bit depths to be practical). The conversion is done with an IDT or input transform. This is doing a very similar thing to a technical conversion LUT, but performing the calculations on the fly, rather than precalculating and interpolating as in a LUT.

As I mentioned, AP0 looks weird seen untouched on a monitor (I wrote an app called LUTCalc in which you can see the effect), and scene linear also looks terrible (and will clip) on a monitor designed around a gamma (ie all of them), so ACES applies another transform - an 'RRT' - which brings things to a more sensible, consistent 'display referred' space, from which an 'ODT' or output transform tunes it for the particular end application relative to the thing you are seeing on your edit monitor. In fact, there is another stage between the IDT and the RRT, which is an 'LMT' or look modification - the basic 'look' to start a grade from.

When you play with ACES, you are actually working between the IDT and the LMT, on the linear scene referred data. But what you see as you make adjustments is the consequence of the LMT and ODT applied as well. It's juts done behind the scenes so the user doesn't need to be aware of the tedious calculations and can just twiddle knobs and push sliders. ;-)

Now for the non-ACES version. Do what you suggest in 1. The LUT is applied first. In something like Resolve, the internal calculations are floating point, so provided the LUT doesn't clip important stuff internally, as this point you will not have lost any picture information (other post software varies in it's handling). Using the example of a Rec709 LUT, if you have you monitoring setup correctly, now do all your corrections after the LUT. WYSIWYG.

Now, a 'Rec709' LUT may be very strict with the gamma (eg the Resolve input LUT) and have the pure gamma curve with no knee, clipping on the monitor (but still storing the highlights as floating point data), or it may play a bit looser, with some kind of knee or tweak of the contrast, plus adjustment of the colour space side of things. LC709 and LC709-Type A are examples of this and can be thought of as equivalent to the ACES LMT. The upshot though is to have a nice looking base picture from which to work on with Rec709 (or possibly Rec2020) monitoring.

So what about the application-specific tuning? The 'ODT' in ACES. Well, then you can apply a second LUT. IF you have worked with Rec709, your end result will be Rec709 within legal (or possibly data) range. Once you are done grading, clipping stuff you are no longer interested in doesn't really hurt, so you can apply a LUT which takes, for example, Rec709/Rec709 values and spits out DolbyPQ/Rec2020 values. In Resolve, there are a whole set of these for different desired nits levels for 'bright white'.

Mind you, most people won't be needing to prepare alternate output versions of their productions (much as we'd all love to think that a cinema release would be a possibility ;-) ). In that case apply base LUT / look (can generally be done en masse to clips) then grade till happy then output will be plenty.

Having rambled for ages again - sorry - ACES has been developed over a long time to pull disperate cameras to a consistent base, then grade within a consistent viewing environment, then output consistently and appropriately for a specific application. It is very clever, very good to be familiar with and, by hiding the tricksy stuff will probably eventually be the basis for how most or all post software works in relation to log, raw and HDR material. For now, a simplified alternative is apply look / LUT (matched to the MLUT used for location viewing), polish as needed, output,

Ben
 
Ben - as you might have read in one of my posts, I'm a somewhat "special editor" in that - for many reasons I'll not elaborate on at this point - I'll be editing with my own monitoring device in mind, and this device isn't an $$$$ pro monitor, but a 55" Samsung "Quantum Dot", HDR1000, wide color gamut (whatever Samsung means by that in their marketing linguo) UHDTV which is hanging right above my desk (10 bit of course - not my desk:), my workflow hw). I like the workflow you propose, ie. starting with applying LUT in resolve to my FS7 log footage, " then grade till happy then output" :) Two questions though:

1. By "grade till happy then output", I'm supposed to get pleased with the output on this specific monitor - and once I am, all its advantages over a $500 desktop monitor with 8-bit panel will be used fully; is that right?

2. If I wanted to add some effects missing from Resolve, and some music score I can do in Vegas Pro so easily - can I switch to it without losing any video information? I assume I'll have to run it in 32bit/ACES mode for that?

3. Which format of a PC-playable file should I render to for keeping all the quality?

TIA.

Piotr
 
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