Any comment on using ACEScg in Nuke, and why there is no Rec709 rrt? From reading the ACEScg white paper, it does seem there is just a matrix that can be used. Also I notice OCIO ColorSpace has ACES to rrt Rec709.
On 6 July 2015 at 13:55, Deke Kincaid <[email protected]> wrote: > Just a note to add to Matt's post. Do not use the ACES or IIF included > with Nuke as it is 3 years old (ACES v0.1.1). Get the ACES 1.0 OCIO > profile off the Academy site (it links to HP's current fork of the OCIO > configs on github). > > > http://www.oscars.org/science-technology/sci-tech-projects/aces#field-tabbed-content-tab-1 > > That should be it. One possible hitch -- I think the EXR writer doesn't >> know that you're in ACES so won't write the metadata about ACES. (Anybody >> know if that's still the case?) > > > Nuke does not support writing the "chromaticities" metadata at the moment > and you can't simply use a modifyMetadata to add it as it's not a simple > string. Also we do not yet support the ACESClip sidecar file at this > moment either. > > -- > Deke Kincaid > Media & Entertainment OEM Development Manager > The Foundry > Skype: dekekincaid > Tel: (310) 399 4555 - Mobile: (310) 883 4313 > Web: www.thefoundry.co.uk > Email: [email protected] > > On Mon, Jul 6, 2015 at 1:27 AM, <[email protected]> wrote: > >> Hey Matt, >> >> I have to test some of those things and will get back to you. Or >> hopefully not. :) >> This is just a quick Thank You for your thorough explanation. >> >> Greets, >> Igor >> >> >> >> Am 05.07.2015 10:05, schrieb Matt Plec: >> >>> On Fri, Jul 3, 2015 at 10:04 PM, <[email protected]> wrote: >>> >>> Hey guys, >>>> >>>> I am trying to wrap my head around ACES. >>>> >>> >>> I'm sure you're not the only one. I have heard that before... Here's >>> the basic idea: >>> >>> First off, for anyone who hasn't thought much about color management >>> in general, why does it matter? >>> >>> When you work with color in the computer it's just numbers, so we need >>> a way to define what color, in some absolute way, [1.0, 0.0, 0.0] >>> means. >>> >>> What do you need to turn a [1.0, 0.0, 0.0] from Nuke into to see the >>> same color projected by a DCI compliant monitor as you see on your >>> workstation monitor? Or if you've got an sRGB JPEG and a REDcolor clip >>> does the value [1.0, 0.0, 0.0] mean the same color in the scene? (No!) >>> A colorspace specification like sRGB, rec709, AdobeRGB, and ACES >>> defines that. Which in turn makes it possible to transform color >>> values between one space and another. >>> >>> There are two key parts to a colorspace: the colorimetry -- the >>> primaries & white point that specify the hue/shade intended by a color >>> value -- and the transfer function (or encoding), which specifies how >>> the increase/decrease of values is encoded -- log, some gamma, etc. >>> >>> When you read an image into Nuke you might have noticed that the >>> (so-called) colorspace knob only defines the encoding. As a result, >>> there's sort of a built-in assumption that you are working in the same >>> colorimetry as your input images (and that they are all the same) and >>> all you need to specify is the transfer function to make them linear. >>> That was true (ish) when everything came from a film scanner and went >>> back out to a film printer. (err... well, let's not get into that.) >>> And we hack around it with Colorspace nodes. >>> >>> Luckily, by the nature of digital capture devices, their colorimetry >>> is known (even if only to the manufacturer) so a translation to well >>> known spaces can also be defined. Then as a practical matter we just >>> need to pick a working space to transform different sources into for >>> processing and back out of for display/delivery. >>> >>> In the past we knew what the "from" was based on file type, headers, >>> etc. (hopefully) but there was no well-defined standard "to" (though >>> it's essentially de facto been sRGB/rec709). >>> >>> Enter ACES. >>> >>> So, from what I understand ACES gives us on hand more gamut and on >>>> the other hand it is a way to bring footage together from different >>>> sources more easily. >>>> That sounds good, right?! Ok, but I never used that kind of >>>> workflow, and it does not seem to be that trivial. >>>> >>> >>> I think you'll be surprised. Conceptually it actually isn't really >>> much more than what happens now in Nuke. >>> >>> By default when you read an image in it goes through a process to >>> linearize it. When you write it out it goes through another process to >>> log or gamma it. If you're working in ACES that process just involves >>> more math to change the colorimetry in addition to the encoding. For >>> you as a user it's just more manual because of outdated assumptions >>> built into the Read/Write, and there are some gotchas to watch out >>> for. >>> >>> Since the Read & Write only do a 1D LUT for colorspace, you need to >>> use OCIO nodes to do the input and output colorspace transform >>> instead. Which means setting the Read/Write colorspace knobs to >>> linear. But if you do this and you're converting to/from log with >>> OCIOColorSpace or OCIOLogConvert then the Write can't autodetect that >>> you're writing log and set the dpx headers correctly, so you need to >>> set the transfer knob manually. >>> >>> In the Project Settings' OCIO tab, pick the ACES config and set the >>> viewer LUTs to use OCIO luts so you get the ACES conversion to >>> rec709/sRGB for display on screen. >>> >>> Congratulations, you're working in ACES. >>> >>> The scenario: >>>> I've got R3D files which I push through hiero to generate openEXRs. >>>> Problem I've got is I do not see an option to set the exrs for ACES, >>>> like in REDCINE where I can specify that in the export settings. Ok, >>>> comparing those two (redcine aces exr vs hiero exrs) the difference >>>> is visible, most prominent the reds seem more pushed or saturated in >>>> a non-aces exr. >>>> >>> >>> If you've selected ACES for your OCIO config, then your inputs are >>> converting to ACES on read and the colorimetry of the output EXRs will >>> be ACES since there's no conversion when writing to EXR. >>> >>> Now my questions: >>>> When I process them as aces, I also need a display LUT so that I see >>>> the right output, right? Is this provided with the OCIO Aces Config? >>>> Have to take a look at that. >>>> >>> >>> Yes. >>> >>> What do I do with CG content? Do I apply a LUT in Maya, or even to >>>> the render itself? Or do I treat it as usual and just transform the >>>> color into ACES space? To what do I render? ACES or nonACES plate? >>>> Do I treat CG simply as scene referred light? >>>> >>> >>> You'll need to convert your textures from whatever space they're in >>> now to ACES, either by converting the files or setting something on >>> your texture reads, like you'd do to linearize them. I don't know >>> about others, but MODO supports OCIO so you can pick the ACES config >>> and then just make sure your texture inputs have the right colorspace >>> set. And of course view through the ACES sRGB or rec709 LUT so the >>> image gets translated properly for your display. Essentially the same >>> as in Nuke. >>> >>> How do I export in Nuke exrs in aces? Simply set to linear and >>>> everything is fine, or more magic sauce? >>>> >>> >>> That should be it. One possible hitch -- I think the EXR writer >>> doesn't know that you're in ACES so won't write the metadata about >>> ACES. (Anybody know if that's still the case?) The files are EXRs just >>> fine of course but anyone else relying on that metadata to identify >>> them as ACES won't find it. Maybe someone's got a ModifyMetadata node >>> they could share that puts the right stuff in, to chain in before the >>> Write? >>> >>> Hope this helped! >>> >>> I am a bit confused, and any (non-technical as possible) >>>> explanation, tip, link, whatever is highly appreciated. >>>> >>>> Thanks in advance, >>>> Igor >>>> _______________________________________________ >>>> Nuke-users mailing list >>>> [email protected], http://forums.thefoundry.co.uk/ >>>> [1] >>>> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users >>>> [2] >>>> >>> >>> >>> >>> Links: >>> ------ >>> [1] http://forums.thefoundry.co.uk/ >>> [2] http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users >>> >>> _______________________________________________ >>> Nuke-users mailing list >>> [email protected], http://forums.thefoundry.co.uk/ >>> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users >>> >> >> _______________________________________________ >> Nuke-users mailing list >> [email protected], http://forums.thefoundry.co.uk/ >> http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users >> > > > _______________________________________________ > Nuke-users mailing list > [email protected], http://forums.thefoundry.co.uk/ > http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users >
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