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    #31
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    Quote Originally Posted by balazer View Post

    If you have a LUT that goes from a camera log space to a display color space, it's doing color space transformation, display rendering, and maybe also changing the colors. There's no good way to integrate that kind of LUT into the Logarist workflow. Logarist depends on having an extended highlight range and scene-referred color. Once you're in the display color space, you lose those.
    This is exactly the case and what my worry was when I asked the question. I guess one thing that would solve the problem would be a special Logarist LUT replacing the existing BT.709 LUT that you provided (second of the pair) which would reverse the first Logarist LUT into for example Sony LC709 instead of BT.709. In other words, one could still get benefits of Logarist without having to use the result of BT.709 reverse LUT as a starting point.
    Last edited by broughtonfilm; 01-18-2017 at 10:12 PM.


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    #32
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    The problem with all those camera log to display LUTs is that they do nothing to help with the color correction process. The camera log space and the display color space are both really sub-optimal for color correction. There's nothing magic about the look of the Sony LC-709 or LC-709TypeA LUTs. They're just BT.709-ish, with reduced contrast and saturation. They're really only good for previewing. I think you'll forget all about them after you get used to Logarist.


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    #33
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    Quote Originally Posted by balazer View Post
    The problem with all those camera log to display LUTs is that they do nothing to help with the color correction process. The camera log space and the display color space are both really sub-optimal for color correction. There's nothing magic about the look of the Sony LC-709 or LC-709TypeA LUTs. They're just BT.709-ish, with reduced contrast and saturation. They're really only good for previewing. I think you'll forget all about them after you get used to Logarist.
    I'm actually testing it now. I guess I'm probably used to my usual workflow which uses one of the Sony LUTs you mentioned and need to test Logarist more extensively but so far I can't get the highlights to have a gentle rolloff using Logarist, not without additional adjustments and still can't get them to look as good as in my usual workflow. They also tend to look oversaturated. Not sure why but noise seems to be more visible despite a more contrasty look of the base starting point as compared with a straight LC709A LUT. I do see how adjusting exposure with the offset wheel works linearly. This will be especially an advantage when dealing with Slog 2 footage which requires lots individual lift/gamma/gain adjustments, more so than Slog 3.


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    #34
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    How do these LUTs make color correction better? Here's a concrete example. Say you underexposed a shot by 2/3 of a stop, by which I mean that if the ISO setting or the exposure would have been 2/3 of a stop higher, the shot would have turned out just how you wanted. Using normal color correction tools, only a specially shaped curve could fully correct that. Using lift/gamma/gain or some other shadow/mid/highlight tools you could come pretty close, except in the highlights near the clipping point. In Logarist, you just drag the offset slider up until the image is as bright as you want. It's a simple one-dimensional control, instead of a complex curve or separate low/mid/high adjustments. The result in Logarist will be nearly identical to increasing the ISO setting in the camera.
    How does this differ from the exposure control in Resolve or Lumetri?

    To correct white balance with traditional tools, you need to correct the shadows, midtones, and highlights separately if you want to achieve the same color balance across the whole image. In Logarist, it's just one color control for the entire image.
    Same question?

    Color is baked into a non-raw file. But when you know how the camera did its transformation from raw sensor channel values to color values, that transformation can be inverted, taking the image from colors back to the raw domain. That's what I do here, though not all the way back to raw. I transform the camera's color values back to scene referred linear color, which is one step removed from raw sensor channel values. Of course the end-to-end transformation is not lossless. It's not the same as having a raw image. It's been de-bayered, sharpened, noise reduced, clipped, and quantized, and compressed. But that doesn't mean it's bad.
    But it actually is kind of bad. As you state, we're STARTING with a mangled 8-bit image. The majority of the data has been thrown away, it can't be recovered. (It can be synthetically reconstructed to varying degrees of perceptual success, but that's not what you're suggesting.)

    A 10-bit uncompressed camera log recording isn't raw, but anyone would be hard pressed to tell the difference. In terms of color correction, a high precision log space with an extended range of highlights gives you nearly everything that the raw image had.
    No doubt, but again, that's not what we're starting from with these cameras. And if we were, we'd just work in that space, not yours.

    To use still photography as an analogy, would you shoot JPEG and bring that into Photoshop for color correction? It's far better to shoot raw, use Adobe Camera Raw as your first pass, and then make additional changes in Photoshop. Logarist isn't quite the same as shooting in raw, but it's closer.
    To extend your analogy, you seem to be suggesting that one could take that compromised JPEG, transform it into a different color space, and somehow get back to the RAW image. You can't. Too much has already been lost.

    No one is twisting your arm here. If your style of shooting lets you get the color and exposure almost perfect in the camera and you already have LUTs that give you the look you want, you're not going to benefit much from more advanced color correction tools. If you're comfortable working the way you have been, by all means keep doing it. I can't convert all the skeptics. I just know that for me, this new way of working has proven much better, and I wanted to share that with people.
    I want to understand what real world benefits I could gain from this workflow. I think there are some minor benefits...i.e. certain transforms are more straightforward depending on the NLE...but you're clouding those benefits by using language that seems to claim much more. Maybe that's just an unfortunately byproduct of trying to keep the explanation simple, but it does make the skeptic in me come out.

    Here's a real world example that will work with a RAW file, and will fail with Logarist:

    1. Use a camera supported by Logarist and that can shoot a RAW still,
    2. Set-up a color chart under low tungsten light. (Necessitating an ISO high enough to introduce noise.)
    3. Underexpose by a stop
    4. Set your white balance to daylight.

    (I use this example because I can't count how many times I've had to work with event footage shot this way by accident.)

    5. Record video using a normal profile, as recommended in the Logarist guide.
    6. Shoot a RAW still. (Again, high ISO, underexposed, wrong white balance.)

    If you do this, you WILL be able to recover the RAW file with reasonably good results. Most of the colors on the chart will be able to be pushed into place close enough to perceptually match a daylight shot. You will NOT be able to do so with the video, whether you use the Logarist "system" or not. The baked-in color errors are too severe. The color information was destroyed, there is nothing to recover.

    Yes, this is a somewhat extreme example. I would not expect it to work, no more than I would expect it to work with a still JPEG. I mention it here because when you make comparisons to Lightroom and RAW, I think you implicitly invite such hope.


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    #35
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    Quote Originally Posted by broughtonfilm View Post
    so far I can't get the highlights to have a gentle rolloff using Logarist, not without additional adjustments and still can't get them to look as good as in my usual workflow.
    I have 8 different highlight handling LUTs there, besides plain BT.709. Try them. If you don't like the way they do the highlights, of course you can roll them off however you want with a curve.


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    #36
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    joe12south, I never claimed that 8-bit compressed video will be as good as raw. I only claim that the color correction can be easier and more accurate and more like what you can achieve with a raw image.

    Logarist doesn't care if you record in 8 bits or 10 bits, compressed or uncompressed. Whatever you record in, that gets decoded to 32-bit floating point, and that's what Logarist works with. And yes, it's still subject to the limitations of your camera's recording, with its noise and quantization and clipping. Logarist doesn't care about any of that. It's just color values to Logarist, just numbers representing colors.


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    #37
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    Balazer,
    My encouragement is to be careful about how you describe your product. From your website:

    Logarist enables the same types of corrections that you can achieve using raw images in Adobe Lightroom, but without the need to shoot in raw, and right inside your video editing application.
    A reasonable person could read that the wrong way.

    I think you would also benefit from being more straightforward in describing the characteristics of the LUT. After all this back and forth, it sounds like:
    1. Linear response curve
    2. Wide gamut
    3. Some amount of camera specific adjustments to get them all to the same point, but I'm unclear about which differences you are accounting for?


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    #38
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    Balazer,

    Any chance Logarist would work with Fusion or could be adapted to work in Fusion? I tend to use that for compositing and fine tune processing of material.


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    #39
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    I gave it a try and I find it pretty straightforward to use it in DaVinci, expecially when you put all the nodes that you need in a powergrade.


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    #40
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    I don't know about Fusion. I've never used it.


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