Cinelog - True logspace conversion for DNG and CinemaDNG footage

[swinxx]

@andy600.
im looking forward to handle the green problem but unfortunately i think this is not possible.

[kgv5]

@Andy600 - i have such a question -  i am trying to set LUT for scopes in resolve 11 for proper image balancing but i have those options greyed out (4 tabs which you marked with the red box in "scope and viewer LUT" section) . I set input and monitor LUTs according to your tutorial, could i miss something? Second thing - what is the difference between REC709 wide DR (v1 and v2) and REC709 FM wide DR (v1 and 2)? Is it right to use one of them for balacing shoth versus REC709 FULL? THanks

[Andy600]

@swinxx - It's possible to fix using a secondary color correction but not so easy with a primary grade as changes to the green channel will likely impact skin tones - but we will look at a few methods in a tut soon.

@kgv5 - I'll have to take a look at Resolve Lite (which I don't have installed at present). Can you use the following work-around for the moment?-

Instead of adding the Cinelog-C to REC709 to the monitor slot, add it to the 3D output Lookup Table slot instead (this will make Resolve's monitor and Scopes see a REC709 signal).

Make your white balance corrections (if needed)

Just before rendering go back to the Lookup table panel and remove the Cinelog-C to REC709 Lut - This will mean your rendered video will be Cinelog-C.

As for the Wide DR and FM luts - Wide DR v1 has highlight recovery, Wide DR v2 has highlight and shadow recovery - These only affect the output gamma of the signal but have the same RGB primaries and white point (i.e. REC709).

Both Wide DR luts give you a little more room to adjust the levels/curves and both usually require more work. They are OK to use when white balancing the image BUT I would recommend using the Cinelog-C to REC709 lut as it has a well balanced S-curve.

The FM versions use Alexa Film matrix primaries. They are slightly more saturated and vibrant, plus produce hue twists for greater color separation. They have a D65 white point but I would not use these for balancing, they are more of a look. The Film Matrix is primarily used in conjunction with Print Luts (PFE) but I've built REC709 versions simply to give you another choice.

If you simply want a good REC709 output use the Cinelog-C to REC709 lut.

FYI - REC709 (it's proper name is ITU-R BT.709) is actually not a look. It is the SMPTE specification for HDTV display.

REC709 has a D65 white point and a recommended gamma of 2.35 (but this usually varies between 1.9 - 2.4). The transfer curve of REC709 is steep and clips - this is why we use an S-curve. The S-curve pulls down the highlights and pulls up the shadows, yet still has good contrast in the midtones.

In simple terms, the REC709 colorspace can be thought of as a small container (with ~6 F-stops, a specific white point and defined RGB boundaries) into which you are trying to squash a much bigger signal (i.e. your camera's ~11 F-stops of DR), yet still retain a good balance between contrast with minimal or no clipping.

[baldavenger]

@andy600.
im looking forward to handle the green problem but unfortunately i think this is not possible.

Hi swinxx, can you please post a few examples of bad greens (foliage), and then perhaps some examples from tv or film where you feel it looks right?  I find myself paying more attention to the quality of foliage colour as captured on screen, especially if shot on an Arri Alexa.  From my limited experience so far I find that LUTs emulating Kodak Vision 3 50D 5203 negative stock then to produce more pleasing looking greens.  Grass in general tends to look better when bluer light falls on it, thereby partially neutralising the yellow content and allowing the true green saturation to come through.

[DeafEyeJedi]

Interesting point @baldavenger & @Andy600 as always thanks for the follow up on these important factors!

[kgv5]

Instead of adding the Cinelog-C to REC709 to the monitor slot, add it to the 3D output Lookup Table slot instead (this will make Resolve's monitor and Scopes see a REC709 signal).....

Thanks for the explanation Andy and i will surely try your work around.

[Andy600]

@swinxx - re: green channel/grass/foliage. Try the new Cinelog Universal Film REC709 LUTs in the Lut bank. They should help a lot

[DeafEyeJedi]

@swinxx - re: green channel/grass/foliage. Try the new Cinelog Universal Film REC709 LUTs in the Lut bank. They should help a lot

Good call @Andy600!

[swinxx]

@Andy:

greenproblems:

thx for the new luts but they do not work in my case.
i hate to shoot in the middle of a sunny day with so many harsh lights but in this case, the time was limited so we have to take this shot. i know that it is possible to mangle the colors in resolve but i hoped that a lut solution could probably safe a lot of time. perhaps you can have a sneak look at the dng which is here:
https://copy.com/XzDWmt6JGpJk0n7v

thx. sw

[Andy600]

@swinxx - The raw file looks OK and greens look quite nice under the Universal Film LUT on my FSI monitor and Panasonic Plasma.

Can you export a frame from Resolve with the BMD Film to Cinelog-C and Cinelog-C to REC709 luts applied? I think your issue may be white balance related but I don't know what you are seeing on your monitor or what your color temp/tint settings are. Also, what kind of look are you trying to achieve? Do you have a reference image from a film etc?

Did you shoot a neutral reference in any shots? i.e. a gray card, colorchecker chart etc?

[marekk]

Hi Andy600.. I've got one question regarding Cinelog-C workflow. I would like to make timelapse video but single frame will be a merge of 3 images (luminosity masks). Then I would like to export final frame to TIFF. I would like to export final sequence to prores 4444 Cinelog-C. Is there a possibility to convert sRGB to Cinelog-C ? What color profile should I choose in Lightroom ? Standard or Neutral ? I would like to correct only a white balance in Ligtroom and maybe some lens settings..
marekk

[Andy600]

Hi @marekk,

I'm not personally a Lightroom user but you can certainly use the ACR version of Cinelog-C to export a log image from Lightroom. Technically you can transform from sRGB to Cinelog-C but I would not recommend it as the transfer functions (i.e. the remapping of curve code values) are not compatible and the signal would be clamped.

LR does not support LUTs but it does support Digital Camera Profiles.

Personally, I would do this kind of thing in After Effects but the initial linear-to-log conversion is still possible in Lightroom. I'll assume you are working with raw images (not baked JPEGs etc) in Lightroom and I suggest the following workflow:

Make your white balance, lens corrections and exposure compensation (if needed) for each image using the Standard profile in LR - this is just so you can judge the balance better because it's hard to do this looking at a very flat log image.

Make your luminosity masks (I haven't done this part in LR so I can't be sure how it works) so you end up with your 3-into-1 shot composites.

When you're happy with the balance, change the profile for each shot to Cinelog V3.0 (there are V3.0 profiles for most cameras in the Cinelog-C ACR pack). This will give you a log image with sRGB primaries and should retain any adjustments you made to white balance etc.

Export your composites to 16bit TIFF image sequences.

In AE, PPro, Resolve etc: Import your image sequence and add a Cinelog V3.0 to Cinelog-C transform (in AE/Premier this would usually be done with the OCIO plugin using the Cinelog-C configuration and in Resolve or other NLE's you would use the Cinelog V3.0 to Cinelog-C LUT). You can then use any of the Cinelog REC709 or Film Look luts.

You don't have to transform to Cinelog-C. You could transform to other colorspaces i.e. if you have other lut packs like Impulz, Koji etc.

[Andy600]

@marekk - Also, we should be able to build an ICC profile for Lightroom that defines the Cinelog-C colorspace (it would appear along with sRGB, proPhoto etc) but I need to look into LR architecture first. If it's the same as Photoshop it shouldn't be a problem.

[QuickHitRecord]

Andy, I would really appreciate it if you could do a tutorial on your site about using Cinelog-converted footage with FilmConvert (maybe also Koji, Osiris and others as well). I've experimented a lot, but I still don't think that I am tapping the full potential of this combination.

[Andy600]

@QuickHitRecord - There will be color grading tuts and we will look at how Cinelog-C can be used to bridge to other LUTs and app presets from other companies. Cinelog-C is essentially a colorspace management system that allows you to target a defined colorspace. For instance, if you have a LUT or a preset that expects Canon Log DCI P3+ colorspace (i.e. from a C500 set to record DCI P3+), you can transform the colorspace and log transfer curve of your 5D Mark III DNG images to Canon Log DCI P3+. Think of it as like being able to fit a square peg in a round hole by mathematically transforming the square peg into a round one with the exact dimensions of the round hole.

Obviously, we have no control over how other vendors produce their LUTs/Presets/Profiles etc and can only hope they work within industry standards (such as SMPTE standards, Ampas ACES, OpenColorIO etc). SMPTE standards, color management frameworks and the manufacturer's own publications (i.e. those from Sony, ARRI, Canon etc) are there to define the exact chromaticity and curve/formula or transfer function of each colorspace and everything should be checked and measurable. Any app that can assign a colorspace or transfer function is built to these standards. If a vendor has simply made a few grades and exported these as LUTs to sell without any thought as to the source footage then there is no telling what will happen - sadly, there are quite a few who do this and nearly all of them get it wrong.

Everything we do that could be classed as a 'look' is always from Cinelog-C colorspace and we offer a means to transform most other colorspaces to/from Cinelog-C.

I think colorspaces, log formula, LUTs, Camera Profiles, cameras etc are also things we should go into more detail about because there is a lot of confusion out there. I have a huge list of topics to cover and will work through them. I'm aiming for 1-2 tuts/articles a week but bear with me
 

[swinxx]

But andy: am i missing something??
In my case I have converted the canon 5d material in davinci from bmd film (cause bmdfilm4k is a bit darker) to cinelog-c.
In the next step - just out if interest - i converted it to bmdfilm.
As the real bmdfilm camera provides different sensor output, the raw material looks diffrrent. So in my case the material looks the same as the source material, so when i take a bmd lut, eg a bmdfilm to rec709 lut, it looks wrong. What i expected was the transformation to bmdfilm material (colorwise) when using the cinelog to bmdfilm lut. So thats not the case. Can you explain that please. Thx

[Andy600]

@swinxx - I think you must be doing something wrong but I can't say exactly what unless I can see what you are seeing. The Cinelog-C to BMD Film LUT is an exact inversion of the BMD Film to Cinelog-C LUT. Are you sure you are using the Cinelog-C luts and not any of the older Cinelog LUTs?

To test the transform for yourself - Import a shot and set the camera raw panel to BMD Film with Highlight Recovery switched on. Then can create 2 nodes. Add BMD Film to Cinelog-C to the first node and Cinelog-C to BMD Film to the second then press ctrl+D to bypass the nodes - The image will not change i.e. the first LUT cancels the second LUT. If you do see a change double check you are only using the new Cinelog-C transform luts (they all have [TRANSFORM] in the name). You don't even need a calibrated monitor to check this as the Scopes in Resolve will show you what is happening - but you really should be using a good calibrated monitor when color grading.

BMD Film colorspace is not published. We had to reverse engineer it using the DNG matrices of DNG files from the Cinema, Pocket and 4K cameras. Everything is mathematical i.e. we haven't had to tweak it by drawing curves or making hue/sat adjustments with color wheels. We use the transfer function (the curve) of BMD Film (the same BMD Film to Linear curve that is in Resolve) and a 3x3 RGB matrix to map the color to/from CIE XYZ. We tested everything through ACES to be 100% sure.

BMD Film only looks darker because it's transfer function has less dynamic range than Cinelog-C. The exposure offset between a BMCC shot and a 5D mark III at 800ISO is ~-1 F-stop so you will need to increase exposure roughly 1 F-stop for 5D mark III footage. Exposure in Resolve is a non destructive linear function, independent of gamma.

A raw DNG image has NO colorspace. The colorspace is prescribed using single or sets of color matrices that map camera RGB pixel values to CIE XYZ at 1 or more illuminants. CIE XYZ (http://en.wikipedia.org/wiki/CIE_1931_color_space#Definition_of_the_CIE_XYZ_color_space) is the common connecting colorspace used by all (well, most) raw processing apps including Resolve.

A DNG from the BMCC differs slightly from an ML DNG because it has a log-to-linear curve embedded in the metadata (this curve is used only for compression - i.e. compressed CinemaDNG) but the color matrices in the DNG files of BM and EOS cameras map from camera RGB to CIE XYZ. If you are seeing any color/hue difference between the cameras it is due to the sensor. This is what ACES was developed for - to match shots from any camera to a common colorspace and that depends entirely on the accuracy of the Input Device transform (IDT) - Only ARRI seem to have got this part 100% visually accurate so far. We are working on the EOS ACES IDTs

Anyway, sorry for the little detour into color science but I think it's important to at least understand the basics. If you can export a frame (TIFF, DPX, ProRes, DNxHD would be good - not JPEG) to demonstrate what your specific issue is I should be able to tell you how to fix it.

[Kharak]

Nice read @Andy

Thanks

[andresharambour]

Awesome info Andy!

[swinxx]

Sorry, i think you misunderstood my point of view andy.
What i wanted to tell you is that how can you transform a bmd dng and a 5d dng with the same lut to a cineon colorspace?? When i use a rec709 colorspace in resolves raw tab the colors look awful. Isnt it possible to transfer the sensor difference to match the real bmd sensors first..? How can i use one lut for both source material (bmd and canon)? Thats what i can not understand cause the final result (after cineloc-c transformation will look different cause of the different sensor outputs? No?? Hmmm

[Andy600]

@swinxx - I fully understand what you are saying but I think you have the wrong idea about raw images and colorspaces.

Cinelog-C does not transform the DNG itself. It transforms from the colorspace to which the DNG has been debayered. In Resolve we transform from BMD Film and BMD Film 4k.

The DNG has no colorspace of it's own but has color matrices that tell the raw reader (in this case DaVinci Resolve) how to map the camera's RGB pixel values to CIE XYZ colorspace. It is the BMD workspace that is the colorspace.

Put in simple terms - Resolve reads a DNG and performs a transform from Camera RGB values to CIE XYZ. It then transforms again to from CIE XYZ to BMD Film colorspace which is a very wide gamut colorspace with a logarithmic transfer function and defined white point - all in a 32bit floating point processing space.

This means it does not matter which camera generated the DNG file so long as the color matrices accurately map to CIE XYZ and this is the reason why I submitted the Adobe color matrices for all MLRV capable cameras to MLV developers a few weeks ago. These matrices have been developed under lab conditions - as have the ones in BM camera DNGs.

Differences in camera color are caused by RGB channel cross talk and noise. A very good sensor such as the Alexa's Alev III dual gain CMOS sensor has very good control over crosstalk and very high dynamic range - this produces a cleaner signal and more accurate color. The 5D mark III sensor is very good but has more crosstalk and noise meaning it does not produce color as accurately as the Alexa - not surprising considering the price difference! A low-end camera sensor usually has appalling crosstalk.

Anyway, what you want to know is if the 5D mark III can produce the same color as the BMD Cinema Camera - The short answer is that it already does in a raw workflow.

Cinelog-C does not support Resolve REC709 colorspace the luts only work from BMD Film and BMD Film 4K.

REC709 is a delivery/display colorspace (you can work in it of course if you are going from raw to deliverable without a digital intermediate like Cinelog-C). REC709 has around 6 F-stops of dynamic range with relatively small RGB chromaticity. This is no good for encoding a digital intermediate and is one of the reasons why log and wide gamut colorspaces exist.

I've had several people ask why can't you use REC709 with linear gamma - well, there is a big difference between scene linear (integer values mapping the whole signal within the containers bit depth) and Linear gamma. Linear gamma REC709 is still REC709 colorspace but has a gamma of 1.0 - It is a tiny colorspace compared to BMD Film and Cinelog-C.

Hope that explains it. I'm not sure I can explain it any easier 

[Andy600]

BTW, if you want to match the color of 2 cameras Cinelog-C can help. Color matching is best done in Linear gamma and requires shots of a Macbeth colorchart filmed by both cameras in the same lighting conditions (ideally the same place, same time, same ISO, same lens etc).

Working in BMD Film colorspace - transform the raw images from BMD Film to Cinelog-C then from Cinelog-C to Scene Linear sRGB you can then use the Colormatch feature in Resolve - setting it to sRGB Linear gamma.

This will shift the colors as close as possible to the RGB values of the color chart patches. You can then apply Resolve's Linear to REC709 1D lut to put the image into REC709 display space. The gamut has already been transformed to REC709 primaries with a D65 white point by the Cinelog-C to Linear sRGB LUT.

[swinxx]

Hello andy! Thx for your detailed description. As a creative user and not a technican, i do not understand everything from your latest posts but!! if it is like you describe, why the hell are visioncolor or other developers developing so many luts (for different cameras)?? If it is all the same in raw, it should be useless.. You only need one film emulation per filmstock..? Visioncolor provides 50different stocks for 20 differen cams (or even more) which sums up to more than 1000 luts!! And there are also canon ml raw luts..(especially for canon raw material). Shouldnt look they similar to the bmdfilm camare material when they are all processed with resolve bmdfilm or bmdfilm 4k..?
Sorry man but i cant get it right in my head.. The material look just different..
So when i apply a cinelog-c lut to material recorded with a bmd cam and compare it and make the same with my canon material the output must look the same?? ( i think my program has bugs then;))
Greets sw

[Lars Steenhoff]

We are working on the EOS ACES IDTs

Thats great to hear Andy!

@swinxx ACES IDTs  are what you need to match the different camera sensors to the same color, then you would not need 1000 luts for all the different cameras.

You could then use the same gradung LUT on all the camera's because they are all converted to the ACES workflow.

Andy please correct me if i'm wrong about this

[Tullen]

Hi Andy.

After two years lurking in the 50d raw forum thread, that then sadly got closed down with the Tragic Lantern issue/dispute, effectively killing the 50D thread here on the forum, I will finally get going with my 50D.

I highly appreciate all the hard work you have done both for 50D and with this Cinelog as well. I really want the best possible picture when it comes to noise, DR, upscaling and debayering (and anything else that I missed).

I could buy the Cinelog package just as a thanks for all your hard work, but of course I hope it to help me get the best out of my camera. And that is indeed my question. How can I post process my 50D raw(MLRaw) files in the best possible way for 1080P? If I would need to buy Cinelog before you answer I can of course do so. Since I have not chosen my work flow yet, please give me the one that you think is best, and I will get the programs necessary.

Best Regards, Tullen