Awesome!
On 29 October 2014 12:50, Simon Björk <[email protected]> wrote: > Hi Håkan, > > thanks for following up on this. You're absolutely correct, in my initial > post I hadn't set the illuminant to D65. Also, I realize the ACES->Alexa > and ACES->sRGB was a bit confusing. The whole reason I became suspicious of > the colorspace node was that I had seen a ACES->sRGB matrix that didn't > match, and then I became worried that the the ACES->Alexa was off as well > (I still haven't found this matrix by the way). > > I didn't follow up on the thread but I actually used Ben's script to do > the ACES->Alexa calculation, and that matched Nuke's colorspace (fairly > close), as well as the official paper (LogC - Usage in VFX > <http://www.arri.com/camera/alexa/downloads/>). Good to see your > calculation as well! It should be pretty safe to assume that the colorspace > works correctly :). > > Best regards, > Simon > > > > ------------------------------- > Simon Björk > Compositor/TD > > +46 (0)70-2859503 > www.bjorkvisuals.com > > 2014-10-29 10:07 GMT+01:00 Håkan Blomdahl <[email protected]>: > >> Also, sorry if I am confused: you write ACES->Alexa and then mention >> ACES->sRGB... >> >> Just to test Nuke ACES->Alexa matrix with some external calculations, I >> have some experimental python code here based on bruce lindbloom formulas >> and using NumPy: >> >> rgbw_ACES = colormatrix.RGBW() >> rgbw_ACES.set_rgbw_xy( 0.73470, 0.26530, 0.00000, 1.00000, 0.00010, >> -0.07700, 0.32168, 0.33767 ) >> rgbw_Alexa = colormatrix.RGBW() >> rgbw_Alexa.set_rgbw_xy( 0.6840, 0.3130, 0.2210, 0.8480, 0.0861, -0.1020, >> 0.3127, 0.3290 ) >> >> # Generate Matrixes to and from XYZ >> M_ACES_to_XYZ = rgbw_ACES.matrix_to_XYZ() >> M_Alexa_from_XYZ = rgbw_Alexa.matrix_from_XYZ() >> >> # Combine Matrixes to one: >> M_ACES_to_Alexa = M_ACES_to_XYZ * M_Alexa_from_XYZ >> print M_ACES_to_Alexa >> >> >> And the result gets close enough: >> My code: >> 1.53820322 -0.3513648 -0.16686751 1.01681111 -0.12917464 0.09536237 >> 0.05995383 -0.01124037 0.88068171 >> Nuke: >> 1.53818 -0.351359 -0.166865 1.01683 -0.129178 0.0953645 >> 0.0599613 -0.0112418 0.880791 >> >> So the Nuke node seems fine. I have not got total control of floating >> point precision, data types etc in my calculations, but it seems to be in >> the ball park. >> /Håkan >> >> >> >> On 29 October 2014 09:41, Håkan Blomdahl <[email protected]> wrote: >> >>> Hi! >>> >>> It looks like on the colorspace node you did, you only changed the >>> primaries to ACES but left the Illuminant to D65 ( instead of ACES ). >>> >>> In which case the matrix will be: >>> 1.53818 -0.351359 -0.166865 -0.129178 1.01683 0.0953645 -0.0112418 >>> 0.0599613 0.880791 >>> >>> Could that be it? >>> >>> /Håkan >>> >>> >>> >>> On 20 October 2014 13:05, Simon Björk <[email protected]> wrote: >>> >>>> Deke: I was sure I that it was in this (very interesting) thread >>>> <https://groups.google.com/forum/#!topic/academyaces/9b4VuqPcOHQ> I >>>> read it, but I'm actually unable to find it at the moment. It was not an >>>> official matrix. >>>> >>>> Ben: Thanks a lot for those links. I will see if I can get your script >>>> working. Interesting about the color temperature by the way, I didn't know >>>> that. >>>> >>>> Best regards, >>>> Simon >>>> >>>> >>>> >>>> >>>> >>>> ------------------------------- >>>> Simon Björk >>>> Compositor/TD >>>> >>>> +46 (0)70-2859503 >>>> www.bjorkvisuals.com >>>> >>>> 2014-10-20 4:44 GMT+02:00 Ben Dickson <[email protected]>: >>>> >>>>> > Can you point to the ACES to sRGB matrix you found? >>>>> >>>>> It'll just be the ACES -> XYZ multiplied with an XYZ->sRGB matrix. >>>>> >>>>> You could use a ColorMatrix node to convert from ACES->XYZ, then a >>>>> second ColorMatrix to go from XYZ->sRGB using the appropriate matrix >>>>> from, say, >>>>> >>>>> >>>>> http://www.brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html#WSMatrices >>>>> >>>>> >>>>> > I've been playing with the colorspace node in Nuke to convert an >>>>> > ACES file into AlexaV3LogC (primaries only). Anyone know if the >>>>> > matrix used by the colorspace node is correct? >>>>> >>>>> Not sure. It might depend how accurate you want to be. If you look >>>>> here: >>>>> >>>>> >>>>> https://github.com/ampas/aces-dev/tree/master/transforms/ctl/idt/vendorSupplied/arri/alexa >>>>> ..specifically this file: >>>>> >>>>> https://github.com/ampas/aces-dev/blob/master/transforms/ctl/idt/vendorSupplied/arri/alexa/AlexaParameters-2013-Nov-13/Alexa_aces_matrix.txt >>>>> >>>>> ..has different matrices for each colour temperature (for when >>>>> converting from Alexa footage to ACES) >>>>> >>>>> More simply, if you just want to do basic conversion from ACES to sRGB >>>>> gamut, then you could use this code: >>>>> https://gist.github.com/dbr/24cfd1033c2d59f263e3 >>>>> (as described above, by calculating the ACES->XYZ matrix then XYZ->your >>>>> target gamut) >>>>> >>>>> >>>>> On 20/10/14 12:01, Deke Kincaid wrote: >>>>> > Can you point to the ACES to sRGB matrix you found? The matrices >>>>> that >>>>> > are published from the Academy are going from XYZ to ACES and vs >>>>> versa. >>>>> > >>>>> > -- >>>>> > Deke Kincaid >>>>> > Creative Specialist >>>>> > The Foundry >>>>> > Skype: dekekincaid >>>>> > Tel: (310) 399 4555 - Mobile: (310) 883 4313 >>>>> > Web: www.thefoundry.co.uk <http://www.thefoundry.co.uk/> >>>>> > Email: [email protected] <mailto:[email protected]> >>>>> > >>>>> > On Sun, Oct 19, 2014 at 5:18 AM, Simon Björk <[email protected] >>>>> > <mailto:[email protected]>> wrote: >>>>> > >>>>> > I've been playing with the colorspace node in Nuke to convert an >>>>> > ACES file into AlexaV3LogC (primaries only). Anyone know if the >>>>> > matrix used by the colorspace node is correct? >>>>> > >>>>> > Colorspace matrix (ACES->AlexaV3LogC): >>>>> > 1.53461874, -0.354506, -0.180112 >>>>> > -0.128879, 1.02594, 0.102936 >>>>> > -0.0112158, 0.0604984, 0.950717 >>>>> > >>>>> > The reason that I'm unsure is that I've seen a ACES->sRGB matrix >>>>> on >>>>> > another mailing list that does not match the values I find in >>>>> Nuke. >>>>> > >>>>> > Best regards, >>>>> > Simon >>>>> > >>>>> > ------------------------------- >>>>> > Simon Björk >>>>> > Compositor/TD >>>>> > >>>>> > +46 (0)70-2859503 <tel:%2B46%20%280%2970-2859503> >>>>> > www.bjorkvisuals.com <http://www.bjorkvisuals.com> >>>>> > >>>>> > _______________________________________________ >>>>> > Nuke-users mailing list >>>>> > [email protected] >>>>> > <mailto:[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 >>>>> > >>>>> >>>>> -- >>>>> ben dickson >>>>> 2D TD | [email protected] >>>>> rising sun pictures | www.rsp.com.au >>>>> _______________________________________________ >>>>> 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 >>>> >>> >>> >>> >>> -- >>> Håkan Blomdahl >>> Filmgate AB >>> >>> Järntorget 3 >>> 413 04 Göteborg >>> Sweden >>> >>> www.filmgate.se >>> [email protected] >>> +46 (0)31- 701 02 00 >>> >> >> >> >> -- >> Håkan Blomdahl >> Filmgate AB >> >> Järntorget 3 >> 413 04 Göteborg >> Sweden >> >> www.filmgate.se >> [email protected] >> +46 (0)31- 701 02 00 >> >> _______________________________________________ >> 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 > -- Håkan Blomdahl Filmgate AB Järntorget 3 413 04 Göteborg Sweden www.filmgate.se [email protected] +46 (0)31- 701 02 00
_______________________________________________ Nuke-users mailing list [email protected], http://forums.thefoundry.co.uk/ http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users
