Author Topic: Cinelog - True logspace conversion for DNG and CinemaDNG footage  (Read 412139 times)

Andy600

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Re: Cinelog - True logspace conversion for DNG and CinemaDNG footage
« Reply #825 on: July 18, 2017, 11:01:36 PM »
@bpv5P

I tried previously to answer your questions in an open and thoughtful manner (even offering you test conversions) yet you chose to take a very negative approach based only on your own assumptions with what I can only assume to be a mindset that is prejudiced against anything that is not open source. You also chose to question the integrity of 2 highly regarded members of this community with this: 

But... I have to ask: is @Danne and @hyalinejim doing some astroturfing for you?

Certainly not! I have never solicited, used or manipulated responses from users, deceptively or otherwise. @Danne, @hyalinjim and others can speak for themselves on this but no users have ever benefited, in any way, through endorsing what I do. Their comments and views are their own.

Over time, Cinelog has received numerous endorsements privately from users, some of whom are highly regarded industry professionals and known for being highly critical but I chose not to use these comments even though I could for marketing purposes for the reasons I stated in my previous reply to you.

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I've noticed you're using some selling techniques (especially social proof and bandwagon bias).
There's nothing wrong trying to sell your products, but I don't like astroturfing and discourse manipulation, and as a open source community we should keep these things out of here.

I had to Google the marketing terms you used.

I agree with the last part of your statement (above) however, in the context of your post, there is very obvious implication of dishonesty directed towards myself, Cinelog and the users you mentioned previously that I strongly deny and take issue with. I am not knowingly using any selling techniques. I do not make spurious claims and I am very open with my answers.

Magic Lantern is an open source project but using it or contributing to these forums has never precluded anyone from discussing or recommending commercial applications or products here except where those products have violated Magic Lantern's licensing or the terms and conditions of this message board.  The fact that the vast majority of users do use commercial software is evident.

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So, if you don't need to achieve the exact same colors between various cameras and don't need all the other stuff (luts and support), there's no advantages? Yes, it's our entire choise to feel we want/need it, but if there's no advantage, why would anyone waste money on it?

Sorry I don't quite understand your logic here. Why would you buy anything that you don't want? Aside from the things you mention (accuracy, luts, support etc i.e. some of the advantages) you should take another look at my previous reply and the responses of others as to why Cinelog is regarded as it is. In addition to that, it provides an effective scene-referred processing capability in an app (ACR) that is strictly display-referred and bypasses any requirement to use image-adaptive filters (that will cause flicker). That might sound like marketing spiel but it is factual.

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Since your choise is to keep color conversion linear, your two points of improvement can me the luma curve and color precision. Most people here don't need that precision in color, so on the luma curve there's no better dynamic range preservation compared to alexa-log (the version implemented on MLVProducer, for example)?

What is your assumption about 'dynamic range preservation' and 'alexa-log' based on exactly?

Alexa Log-C is for encoding the 16bit DGA signal from the Alexa's sensor and not an efficient use of the space for transcoding 14bit MLV (and becomes increasingly detrimental to 12 or 10 bit MLV as it spreads code values too far apart and can increase the visibility of banding).

When it comes to transcoding, my choice (dictated by color science and best working practices) is to keep initial color rendering strict and color manipulation to an absolute minimum, deferring color decisions to later in the pipeline. Basically retaining the maximum latitude in a known colorspace.

You again mention 'alexa-log' but what is that exactly? MLVProducer is a great app that can be used for everything (and there are several others too) but there are quality differences and often issues between raw video debayering and encoding with such apps compared to their commercial counterparts else why would those exist and why would people in their millions purchase them? You might answer with another one of the marketing terms I looked up 'herd mentality' but I know quite a few artists, film makers, colorists and developers who might take offence at such a suggestion as they opt to use commercial tools simply because they get the job done without compromises. The free tools on offer often have short comings and, as I described in my last reply, the limitations in open source raw libraries can restrict or limit development.

I'm not detracting from any OS app developer because I know they can be as dedicated as commercial devs and, if you support them, and their tools are good enough for you then who is going to argue with that? Certainly not me.

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Again, don't get me wrong, I'm not trying to prejudice you or anyone possibly working with/for you. It's just that, if your product has no advantage over a free/open implementation, I think no one should buy it. I can think in a recent example like this: corporations were selling certificate authority for many time; "Let's Encrypt" implement a free/open implementation doing the exact (or better) same thing. Now everyone is going to Let's Encrypt. The same should happen with any product that does not do it's job. Contrary to what marketers say, quality is very important. You can do money with basically anything, but not everything keep itself on top of others if it has no advantages over these other alternatives.

I have stated quite clearly what the advantages are and the added value that comes with Cinelog. If you don't value that then simply don't buy it. 

Regardless of your initial statement above, you seem to have a jaded view towards what I offer but Cinelog is not 'Let's Encrypt' and there is no 'fake news' mentality at work here. Regardless of your insinuations I am perfectly happy to respond here to your questions and will always answer as clearly as I can, within the limits of protecting Cinelog IP. However, if you again choose to imply dishonesty or question the integrity of myself or other users without foundation, I will simply ignore you.
Colorist working with Davinci Resolve, Baselight, Nuke, After Effects & Premier Pro. Occasional Sunday afternoon DOP. Developer of Cinelog-C Colorspace Management and LUTs - www.cinelogdcp.com

DanHaag

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Re: Cinelog - True logspace conversion for DNG and CinemaDNG footage
« Reply #826 on: July 18, 2017, 11:29:25 PM »
Andy600 keeps contributing detailed input about color science, working with ML raw video in post production and shares his ideas for possible improvements of the MLV format. He doesn't only try to sell a product, he shares a hell lot of crucial technical input no one else figured out or at least shared to that degree and detail with the community. No matter if you bought or used any of his products or none, he's helped a lot of users in the past with color correction/grading workflow problems and understanding the concept of color spaces etc. - If you ask him "What's the best way to grade my MLV files without Cinelog", be sure Andy gives you the best answer possible no matter what. He has proven this time and time again on this forum.

Danne

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Re: Cinelog - True logspace conversion for DNG and CinemaDNG footage
« Reply #827 on: July 19, 2017, 12:35:11 AM »
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it provides an effective scene-referred processing capability in an app (ACR) that is strictly display-referred and bypasses any requirement to use image-adaptive filters (that will cause flicker). That might sound like marketing spiel but it is factual.
Yup. Confirmed.

@bpv5P
My answer before was only meant as a quick tip, nothing else. You seemed to need one.
By the way. Here is an open source tip to get you towards scene referred in acr(check link below). You will still have to build the math based log(and put into the dcp file) and account for color but it is a start.
One reason I started poking around with this is actually based on amasement of dynamic range I spotted from cinelog dcp examples.
http://www.magiclantern.fm/forum/index.php?topic=13512.msg172443#msg172443

Andy600

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Re: Cinelog - True logspace conversion for DNG and CinemaDNG footage
« Reply #828 on: July 19, 2017, 02:03:13 AM »
@Danne - Linear in DNGPE only removes the tone curve so it's still producing a display-referred image and can only work display-referred. Try it with a very high DR image and you'll get clipping.

A lot of calculations are needed to get ACR to produce Cinelog-C colorspace for any particular camera (every camera is different) and it simply can't be done with DNGPE because the matrix controls will always snap relative to the internal processing space (Cinelog-C is outside of this) and the curve points are very limited with relatively coarse interpolation so transformed RGB values are not precise enough for an accurate log conversion. The Cinelog curve still uses ACR's interpolation but applied to 4096 control points.

Pulling highlights down with the Parametric curve in DNGPE is really just faking highlight recovery with no real gains i.e. once you render with those settings you are just getting a flattened image with compromised highlights because you have stretched and/or compressed the spread of code values with no mathematical way to get them back. i.e. there will be large differences in the amount of information contained in one stop compared to the next. Some stops will have more information and some much less information than required - this ultimately leads to less latitude but more chance of banding and other artifacts.

Generally speaking, a log conversion will spread the code values more efficiently and equally between all stops and because you know the CVs input and transformed values you can put them back with the inverse, anti-log formula - thus scene-linear (relative to light).

With Cinelog profiles a known RGB value can be input, transformed with the profile and output in AE then reverted to the input value (relative to the CCT) using the math built into the inverse transforms. The gamut transform is calculated dynamically and relative to the user selected white balance settings i.e. it is recalculated continually as you move the white balance and tint sliders making it more accurate for the chosen white balance than a fixed CCT plus I also use ARRI's recommended chromatic adaptation (CAT02) not Bradford for the calculations. Beyond that I can't divulge anything else :)
Colorist working with Davinci Resolve, Baselight, Nuke, After Effects & Premier Pro. Occasional Sunday afternoon DOP. Developer of Cinelog-C Colorspace Management and LUTs - www.cinelogdcp.com

Danne

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Re: Cinelog - True logspace conversion for DNG and CinemaDNG footage
« Reply #829 on: July 19, 2017, 02:17:21 AM »
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Generally speaking, a log conversion will spread the code values more efficiently and equally between all stops and because you know the CVs input and transformed values
You can fit in 4096 points into the dcp profile which in itself is pretty neat. I never seen any dcp profiles from adobe using this. Was it ever intended for this? Now how to get hold of that conversion chart. Would be pretty neat to have lets say cineon dcp in acr  :P

Andy600

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Re: Cinelog - True logspace conversion for DNG and CinemaDNG footage
« Reply #830 on: July 19, 2017, 02:45:49 AM »
You can fit in 4096 points into the dcp profile which in itself is pretty neat. I never seen any dcp profiles from adobe using this. Was it ever intended for this?

No. Check out the DNG SDK for the basics. There are also some undocumented and often illogical things to ACR that dictate what you can and can't do with profiles.

Now how to get hold of that conversion chart.


There is no conversion chart as such only math. I started out with spread sheets then CTL then custom Python scripts but there is still a degree of manual intervention required for building and testing each profile.

Would be pretty neat to have lets say cineon dcp in acr  :P

Cinelog-C is Cineon in terms of gamma already but Cineon without the gamut mapping of Cinelog-C can still clip color. I know because I have extensively modeled, tried and tested each and every log curve and full log colorspaces in ACR.
Colorist working with Davinci Resolve, Baselight, Nuke, After Effects & Premier Pro. Occasional Sunday afternoon DOP. Developer of Cinelog-C Colorspace Management and LUTs - www.cinelogdcp.com

Danne

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Re: Cinelog - True logspace conversion for DNG and CinemaDNG footage
« Reply #831 on: July 19, 2017, 09:05:37 AM »
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Cinelog-C is Cineon in terms of gamma already but Cineon without the gamut mapping of Cinelog-C can still clip color. I know because I have extensively modeled, tried and tested each and every log curve and full log colorspaces in ACR.

Does it mean that cineon gamma acts different from applied as a 1D lut in a nle as opposed to applying the same gamma curve through acr? Color is affected differently/clipped?