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Old 8th February 2019, 19:15   #1  |  Link
FranceBB
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FranceBB LUT Collection

Hi,
LUTs are generally used to grade contents, but they can be useful to do quick and dirt color space conversions, especially in this day and age.
Although a good color conversion has to be achieved manually and/or via algorithms, LUTs can still be helpful; unfortunately, I've seen people selling their LUTs for simple color conversion and it incredibly pissed me off 'cause they are supposed to be free, so today I'm gonna share my LUT collection, hoping that it can be useful to someone.

Before you apply any of my LUTs, remember that although you can apply them at any bit depth, I strongly suggest you to do that with 16bit precision, otherwise you'll get banding and other terrible issues.
LUTs are 65x65x65, which is supposed to be high precision, but some of them are 33x33x33 which is just about right. None of them are 17x17x17 'cause I don't consider it to be accurate enough.

LUTs: Link

- BT2100 HDR PQ to BT709 SDR
- BT2020nc HDR HLG to BT709 SDR
- BT2100 HDR PQ to BT2020nc HDR HLG
- BT2020nc HDR HLG to BT2100 HDR PQ
- BT709 SDR to BT2100 HDR PQ
- BT709 SDR to BT2020nc HDR HLG
- Slog2 to BT709 SDR
- Slog3 to BT709 SDR
- Clog3 to BT709 SDR
- Clog3 to BT2100 HDR PQ
- Clog3 to BT2020nc HDR HLG
- Log-C to BT709 SDR
- Z-Log to BT709 SDR
- XYZ DCI to YUV BT709 SDR
- YUV BT709 SDR to XYZ DCI
- Vlog to BT709 SDR

Images:

HLG1:


PQ1:


SDR1:


-

HLG2:


PQ2:


SDR2:


-

HLG3:


PQ3:


SDR3:


-

HLG4:


PQ4:


SDR4:


-

Slog3 pic1:


BT709 pic1:


-

Slog3 pic2:


BT709 pic2:


-

Slog3 pic3:


BT709 pic3:



How to use my LUTs in Avisynth:

Code:
FFVideoSource("example.mxf")

ConvertBits(16)

ConvertToPlanarRGB()

Cube("C:\Programmi\AviSynth+\LUTs\example.cube", cpu=1, fullrange=false)
Slog3 to BT709
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Last edited by FranceBB; 30th January 2020 at 16:35.
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Old 8th February 2019, 23:24   #2  |  Link
gonca
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Thank you for this.
One question
Should it be fulldepth=true or false
since false would return 8 bit I believe
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Old 9th February 2019, 04:12   #3  |  Link
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Quote:
Originally Posted by gonca View Post
Should it be fulldepth=true or false
since false would return 8 bit I believe
Nope, they both return 16bit, but fullrange=true is for full range (PC Range) sources, while fullrange=false is for limited range (TV Range) sources.
Limited range for 8bit is 16-235, for 10bit is 64-940 and so on.
Full range for 8bit is 0-255, for 10bit is 0-1020 and so on.
It depends on your source, but keep in mind that the majority of sources are TV Range and if you encode something for the TV, it has to be Limited TV Range.
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Last edited by FranceBB; 9th February 2019 at 16:40.
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Old 9th February 2019, 12:37   #4  |  Link
gonca
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My mistake
I originally read fulldepth in your sample script, but after re reading it I realize that it actually says fullrange
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Old 9th February 2019, 14:56   #5  |  Link
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Quote:
Full range for 8bit is 0-255, for 10bit is 0-1024 and so on.
Nit Pick, 1023.

EDIT: Hmmm, I'm wrong too.
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Old 9th February 2019, 16:44   #6  |  Link
FranceBB
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Sorry about that.
Actually, this is the right one, I think (from the Avisynth Wiki):

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Old 9th February 2019, 20:48   #7  |  Link
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these "issues" come from the understanding that 10 bit is 4 times as big as 8 bit so we just have to multiply by 4.

8 bit RGB 255 255 255 as 10 bit is 1023 1023 1023 not 1020 1020 1020 has a very slightly lower brightness and is just 4x the original number.

the correct way to increase 8 bit to 10 bit is taking the first 2 bits from the 8 bit source and add them to the end.

or as an small example:

11111111=255 100 % brightness
1111111100=1020 ~99.7% brightness
1111111111= 1023 100% brightness
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Old 9th February 2019, 21:41   #8  |  Link
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Quote:
Originally Posted by huhn View Post
the correct way
But according to whom? The wiki seems to indicate the other way - simple shifting - is correct. What's the broadcast standard?

And what's the correct way to go back down? Is there bit-ty way to do it, or do you have to divide by 4.0117647059?

And I thought 16-235 was a headache...
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Old 9th February 2019, 22:02   #9  |  Link
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i just ask you a different question who stops you from creating a native 10 bit source with 1023 in it?

a bad way to go back to 8 bit is by removing the last too bits truncation. another one would be dithering.
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Old 9th February 2019, 22:19   #10  |  Link
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Quote:
i just ask you a different question who stops you from creating a native 10 bit source with 1023 in it?
Umm, okay, but my questions weren't rhetorical. Nothing stops you from creating a native 8 bit source with 255 in it, but that is - according to broadcast standards - an "illegal" value.

Quote:
a bad way to go back to 8 bit is by removing the last too bits truncation. another one would be dithering.
Dithering still needs a convention as to what values, integer of fractional, correspond between the bit depths.
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Old 9th February 2019, 22:39   #11  |  Link
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Quote:
Originally Posted by wonkey_monkey View Post
Umm, okay, but my questions weren't rhetorical. Nothing stops you from creating a native 8 bit source with 255 in it, but that is - according to broadcast standards - an "illegal" value.
full range is a thing. computer games work in it it's part of display port and HDMI.

while BD source is all ways limited range this doesn't change that even full range encoding is a thing and totally supported by programs like x264.

and be aware that this is about RGB not YCbCr.
so clearly not illegal
Quote:
Dithering still needs a convention as to what values, integer of fractional, correspond between the bit depths.
does it? how should i even know what an dithering algorithm is working internal. i know it using the "errors" truncated parts to spread noise if it is max 1023 or 1020 shouldn't matter. it will just use what it has available.
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Old 9th February 2019, 22:49   #12  |  Link
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Okay, we're getting off-track. The original point is: the Avisynth wiki says 8-bit 255 is equivalent to 10-bit 1020. You say it's 1023. Who's right?
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Old 25th February 2019, 22:30   #13  |  Link
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FranceBB, thank you!
So.
These are examples with your lut "PQ_to_HLG.cube".
I get a similar result only with the help of a long selection of curves in the plugin "SmoothCurve". Good work.
Attached Images
  
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Old 19th March 2019, 05:59   #14  |  Link
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Quote:
FranceBB, thank you!
So.
These are examples with your lut "PQ_to_HLG.cube".
I get a similar result only with the help of a long selection of curves in the plugin "SmoothCurve". Good work.
Thanks, I tried to tweak things correctly.


Update: Added Slog3 to BT709 LUT

Whenever I work for the News channel or for our Sport channel, I receive footages shot normally, but whenever I work on TV Series, I receive footages shot in Slog3 and I always have to bring them to BT709 to encode everything in a standard old-fashioned FULL HD SDR.
I'm gonna share with you my Slog3 to BT709 LUT as well.



Slog3 first, BT709 second:







Some people may think that it's ok-ish, but slightly dark on some low-light scenes, but actually this is because I added a knee to the curve and there's a reason for that: trying to stay in the Limited Tv Range avoiding clipping.
Let's take a look at this example here with a strong light coming from behind.
Raw footage in Slog3:



If I try to apply a transformation without using a knee, the white level gets too high and I get out of legal range, therefore everything over 235 gets clipped out:



By adding a knee, however, I manage to get thinks right in 16-235 without the need to clip so many details out:



If you take a look at the curve of the transformation you can see how the unclipped one gets so high that it almost looks like a function that reaches a vertical asymptote:



While the knee manages to smooth things out and generates a proper curve:

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Last edited by FranceBB; 24th March 2019 at 05:31.
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Old 24th April 2019, 04:41   #15  |  Link
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Update: Added C-Log3 to BT709 SDR / C-Log3 to PQ HDR / C-Log3 to HLG HDR

I added three new LUTs that are meant to be used by Canon C-300 Camera users.
It's a 4K professional camera that can record up to 12bit with the C-Log3 curve and it can definitely be used for HDR productions and SDR ones alike.
What's interesting about this curve with the C-300 is that it's possible to shoot and then grade it to HDR PQ and get approximately 3500 nits worth of data (I mean, real data).
When I created the LUTs, I tried to keep the BT709 SDR one in range and I applied a knee to get the right values.
As to the HDR PQ one, I left it "unclipped" to 10'000 nits, however you're not gonna get anything over 3500 nits. The reason why I left it unclipped up to 10'000 nits, though, is that Canon might release new cameras in the future that are gonna use the same curve and perhaps they'll be able to get more than 3500 nits worth of data.
As to the HDR HLG one, I had to make a very big compromise, 'cause as you know, HLG has been invented in order to display both HDR and SDR using the same file, which basically means that whenever you make a LUT you have two choices: 1) make it more HDR-like and sacrifice the view of the ones with an SDR TV or 2) make it more SDR-like and sacrifice the view of the ones with an HDR TV.
Since many people still have SDR TVs, my choice (as well as the one of other encoders working in broadcast) is to make it more SDR-like, 'cause this way no one is ever gonna complain.
In order to do so, I had to sacrifice the representation of the black values and of course since HLG is limited to 1'000 nits, I had to lower down the highlights as well.
The result looks good and it's definitely more natural than the SDR, but comparing it to the PQ is... like... you know... not quite good enough, but as broadcaster it's kinda acceptable.

Alright, let me show you the graphs.

Let's start with the C-Log3 to BT709 SDR:





As you can see, the C-Log3 curve is very different compared to the BT709 and it's a curve that it's meant for HDR productions as well, so although it can be used for SDR, the grading should really be done manually on a scene by scene basis, 'cause otherwise you might end up with oversaturated or wrong values.

C-Log 3 to BT2100 HDR PQ:





As you can see, the C-Log 3 curve pretty much resembles the PQ curve, this is also why it's actually pretty easy to map it to HDR PQ BT2100.

C-Log 3 to BT2100 HDR HLG:





As you can see, I tried to keep the HLG curve as tweaked as possible to SDR, which actually limited the quality of the blacks for the HDR viewers. As to the peak, HLG is limited to 1000 nits by definition.
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Old 24th April 2019, 04:41   #16  |  Link
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Alright, let's crack on and view some examples.
You'll find the original C-Log3 footage, the BT709 SDR one, the HDR HLG one and the HDR PQ one.
I tried to keep the BT709 LUT as usable as possible, but limiting C-Log3 to BT709 SDR means that many details are really gonna be clipped out and you can definitely see it from the examples below.
As to the HDR HLG BT2100, it pretty much resembles the BT709 SDR version, but it does show more details, despite being still capped out.
Finally, the HDR PQ BT2100 is the best looking version, with a very natural look and it almost feel like as if you were there for real with 3500 nits worth of data.

C-Log3

BT709 SDR

BT2100 HDR HLG

BT2100 HDR PQ


C-Log3

BT709 SDR

BT2100 HDR HLG

BT2100 HDR PQ


C-Log3

BT709 SDR

BT2100 HDR HLG

BT2100 HDR PQ


C-Log3

BT709 SDR

BT2100 HDR HLG

BT2100 HDR PQ
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Old 25th April 2019, 23:54   #17  |  Link
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Once again, thank you for your contribution
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Old 1st May 2019, 09:13   #18  |  Link
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Perhaps a dumb question: How do people select the "correct" LUT? Is it a matter of personal taste, or do we need reference pictures for comparison?
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Old 1st May 2019, 15:08   #19  |  Link
FranceBB
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Quote:
Originally Posted by Sharc View Post
Perhaps a dumb question: How do people select the "correct" LUT? Is it a matter of personal taste, or do we need reference pictures for comparison?
What do you mean?
Each LUT is a matrix of linear transformation that goes from a curve to the other, which basically means that, depending on your source color curve, you use the one to go from it to your target color curve.
For instance, if you have an HDR PQ video and you wanna go to HDR HLG, you are gonna use my PQ_to_HLG LUT.

If you are asking how to create a LUT yourself, then that's a whole different question and... no, it's not a matter of personal taste only, it's a matter of linear algebra, defined standards and personal taste.
You generally start with a linear conversion from a curve to the other and then tweak it trying to get into the right values according to the standard. After that, you can fine-tune it 'till you'll get something that looks best for your taste, as long as you are still respecting the standards.
Anyway, it really depends on your source and your target, 'cause if you have two curves that are really different one to the other, then you are gonna have to choose which parts of the input you wanna keep while you go to your desired output.
Let's suppose that you have a C-LOG3 in input and you wanna go to BT709 SDR in output; you can basically get the calculations right, but you still have to choose what you wanna sacrifice as the BT709 SDR is able to retain very little informations compared to the input and THAT is a personal choice according to what you think it's best.
When I make my LUTs, I always try to keep as many things as possible and make them usable for pretty much every scenario. Let's suppose that we have a scene with snow, a white dog and the sky: you are gonna have three different tonalities of white, one for the snow, one for the dog and one for the highlights (sky). If you originally shoot in BT709 SDR, you have one of those three tonalities of white clipped out, while if you shoot in C-LOG3 you are gonna have as many details as your camera can get, then, in encoding, you can decide to retain the desired part of the image, with the desired tonalities of white. In this specific case, you wouldn't be able to do it with my LUT, 'cause my LUT is gonna take a decision for you and clip what I thought it was supposed to be an acceptable compromise for every scenario, but it's better to do it manually, 'cause by doing it manually you can choose which things you are gonna preserve for that specific shot.
I hope this answer your question; if you want, I can get into more technical details.

Cheers,
Frank.
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Last edited by FranceBB; 1st May 2019 at 17:44.
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Old 1st May 2019, 15:49   #20  |  Link
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Thank you Frank for enlightening me. Your short tutorial answered my nebulous question about the LUTs nicely

Last edited by Sharc; 1st May 2019 at 15:52.
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