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  1. #1 Log to rec709 
    Senior Member david evans's Avatar
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    I was trying to find the best way to bring the log images from my UM4.6k to a colorspace with the best possible color rendering. Just recently I started using Aces colorspace. It seems more natural to me than yrgb but I could be wrong. Also tried the ofx resolve plugin color space transform. Do you guys usually use these tools or just use the color wheels to level the footage and maybe throw in a favorite LUT? Not talking about grading, just bringing the colors and contrast out the best way possible.

    Thanks
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  2. #2  
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    David, in bringing in your log images to a colorspace, are you doing this through a color chart match or using one of the available LUTs for color rendering?
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  3. #3  
    Senior Member david evans's Avatar
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    Hi eyu

    I started experimenting yesterday with two different methods:

    1- using color space transform in Ofx resolve free plugins. It gets me to a very natural color rendering;

    2- change colorspace in project settings from yrgb to davinci aces. Then, setting the aces input and output from the color managment tab. I like this method very much and i was curious if other people here are using this. I'm sure experienced colorists will just work from a log image and adjust levels and saturation as they please and achieve amazing results, but for a non colorist like me, i really enjoy that a computer program gets me there so I can start grading from there.
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  4. #4  
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    Quote Originally Posted by david evans View Post
    Hi eyu

    I started experimenting yesterday with two different methods:

    1- using color space transform in Ofx resolve free plugins. It gets me to a very natural color rendering;

    2- change colorspace in project settings from yrgb to davinci aces. Then, setting the aces input and output from the color managment tab. I like this method very much and i was curious if other people here are using this. I'm sure experienced colorists will just work from a log image and adjust levels and saturation as they please and achieve amazing results, but for a non colorist like me, i really enjoy that a computer program gets me there so I can start grading from there.
    I don't believe that using color space transform actually normalizes log footage, or that it was meant for that purpose.

    Can't speak to using ACES in Resolve with UM4.6k footage, but it doesn't work well in my view with BMPCC footage.

    The simplest way to normalize footage is to put one of the supplied 3ds lut on the last node of the grade, for converting UM4.6k film (log) to rec 709. This should give you a fairly neutral starting point (with any further adjustments made in previous nodes).
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  5. #5  
    check this test to see difference http://bmcuser.com/showthread.php?17...l=1#post214457
    use color space transform in Ofx to convert BMDfilm to more common color space and LOG gamma, for example to REC 2020 with Cineon gamma.
    use custom generated with LUTcalc https://cameramanben.github.io/LUTCa...alc/index.html to compress color space and LOG gamma without clipping.

    Generate LUT in LUTCalc with settings:
    - input gamma: Cineon or BMDfilm (i prefer work in Cineon gamma)
    - input gamut: rec2020 or any other wide gamut you prefer (you need this conversation because native BMDfilm input color space is missed in LUTCalc)
    - output gamma: Alexa-X-2, Amira709 (developed by Arri) or LC709 (developed by Sony)
    - output gamut: LC709 (actually i prefer Amira709 but some time ago Alexa-X-2 and Amira709 gamuts where temporary removed from LUTCalc)

    if final image too dull or black is too clipped you can experiment Input/Output Range:Legal/Data, but most time its ok to leave it as is.

    This generated LUT will compress all tonal and color information without any clipping.

    in Resolve:

    - add color space transform node to timeline and set input: as timeline and output matched to input in your generated LUT.
    - add one more node with LUT.

    Adjust image with contrast + pivot sliders in the node located before LUT. This way you will get a reach colors and contrast but never get a clipping and ugly video look.

    One more useful trick with LOG footage is that you can mimic Exposure(ISO) RAW slider with gain slider.
    - add color transform node: timeline to linear
    - add one more color transform node: linear to timeline gamma.
    - adjust gain in first node (this will act same as expose/iso)

    Remember that when your image in LOG mode the tools works in different way.

    here are also two articles that helps to understand Sony vs Arri color/gamma compression methods and LUTCalc settings.
    http://www.provideocoalition.com/hac...ony-f-cameras/
    http://www.provideocoalition.com/lut...us-a-free-lut/

    Several years ago, at an NAB focus group, I showed Sony the difference in how Alexa saturates color with overexposure vs. an F55. Or, maybe I should say I showed them how Alexa desaturates color with overexposure: once a hue passes a point at or near middle gray in brightness, its saturation locks and it only gets brighter. Traditional video cameras continue to saturate color as exposure increases until color channels clip, at which point they focus on damage control to prevent highlights from shifting hues.

    Arri emulates film, a subtractive color process where maximum color saturation is found in shadows and mid-tones. Sony works with videoís inherent additive color properties and allows saturation to increase with brightness until a color channel fails. Both systems have their merits, but for an old film guy like me film-style highlights are the way to go.

    To Sonyís credit they responded quickly to my demonstration. Within six months they rolled out the LC709 Type A LUT, which attempts to somewhat emulate Alexaís color response. Itís not perfect but itís a solid alternative to Sonyís traditional broadcast look, which is a bit dated for the digital cinema world I currently inhabit. Bright saturated color may sell TV sets in retail stores, but cinematographers tend to be visually sophisticated craftspeople who find highly saturated colors garish. We prefer subtlety and sophistication in our color palettes. Our job is to tell stories, not sell TVs. LC709 Type A brought Sony a step closer to our world.
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  6. #6  
    I'd go with ACEScct, i use ACES on pretty much everything, have since late 2011 in Nucoda FiulmMaster and Baselight, so about 5 years now.. long before Resolve had the toolset working.

    There'a learning curve to be delt with, many tools do not react as expected in display refered workflows, a bit easier for me as i already used a filmstyle gradeing in Baselight and Nucoda, and although it's poorly and incpompletly implemented in Resolve, flimstyle gradeing can be made to work in Resolve.

    The payoffs for working in scene refered are worthwhile for me

    Baselight has a really good 2 x 1hr presentations on scene refered gradeing on their website, the concepts transfer across to Resolve, even if the tools are incomplete and limited by comparison;


    Part 1: Challenges & workflows for colour management today;
    https://vimeo.com/119143638

    Part 2: Solutions with ACES & Truelight Colour Spaces;
    https://vimeo.com/119143639
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  7. #7  
    Senior Member david evans's Avatar
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    Quote Originally Posted by dermot shane View Post
    I'd go with ACEScct, i use ACES on pretty much everything, have since late 2011 in Nucoda FiulmMaster and Baselight, so about 5 years now.. long before Resolve had the toolset working.

    There'a learning curve to be delt with, many tools do not react as expected in display refered workflows, a bit easier for me as i already used a filmstyle gradeing in Baselight and Nucoda, and although it's poorly and incpompletly implemented in Resolve, flimstyle gradeing can be made to work in Resolve.

    The payoffs for working in scene refered are worthwhile for me

    Baselight has a really good 2 x 1hr presentations on scene refered gradeing on their website, the concepts transfer across to Resolve, even if the tools are incomplete and limited by comparison;


    Part 1: Challenges & workflows for colour management today;
    https://vimeo.com/119143638

    Part 2: Solutions with ACES & Truelight Colour Spaces;
    https://vimeo.com/119143639
    Thanks, I'll watch those videos. Which Aces version do you use on Resolve? On 12.5 I have Davinci Aces and Aces CC, under project settings.

    EDIT:

    Btw, could you say which Resolve tools might react differently in ACES color space? I noticed that the spatial denoiser (or the other, can't remember) seems to create negative pixel effect or something. And which advantages do you feel the ACES color space has?

    Thanks!
    Last edited by david evans; 01-04-2017 at 05:36 PM.
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  8. #8  
    Which Aces version do you use on Resolve? On 12.5 I have Davinci Aces and Aces CC, under project settings.
    i'm curently using 1.0.2 / ACEScct in Resolve 12.5.4

    could you say which Resolve tools might react differently in ACES color space?
    before normilasition LGG, Curves and keyers are a pita.. after normilasition they are the same as YRGB, autocolor is useless in ACES, but i think that's about all - once the image is normilised

    I noticed that the spatial denoiser (or the other, can't remember) seems to create negative pixel effect or something
    negitive pixel values and saturated highlights are ongoing issues, both pretty easly sorted tho, negitive pixels by using a very small value of shadow softclip in the first node, highlights by using the Acadmy DCTL/LMT in linear light, either by applying the LMT tot eh shot in the media pool, or by transforming AP1 to AP0, applying the LMT, and then reversing back to AP1.. i use it in the media pool in Resolve, in the first grade stack in Baselight

    And which advantages do you feel the ACES color space has?
    quite a few, some major points;
    - clean maths = clean images
    - bypassing needlessly compressing the dynamic range
    - ODT's reliably creating outputs
    - great starting point - ACES gets me through a base pass quciker
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  9. #9  
    Senior Member david evans's Avatar
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    Quote Originally Posted by shijan View Post
    check this test to see difference http://bmcuser.com/showthread.php?17...l=1#post214457
    use color space transform in Ofx to convert BMDfilm to more common color space and LOG gamma, for example to REC 2020 with Cineon gamma.
    use custom generated with LUTcalc https://cameramanben.github.io/LUTCa...alc/index.html to compress color space and LOG gamma without clipping.

    Generate LUT in LUTCalc with settings:
    - input gamma: Cineon or BMDfilm (i prefer work in Cineon gamma)
    - input gamut: rec2020 or any other wide gamut you prefer (you need this conversation because native BMDfilm input color space is missed in LUTCalc)
    - output gamma: Alexa-X-2, Amira709 (developed by Arri) or LC709 (developed by Sony)
    - output gamut: LC709 (actually i prefer Amira709 but some time ago Alexa-X-2 and Amira709 gamuts where temporary removed from LUTCalc)

    if final image too dull or black is too clipped you can experiment Input/Output Range:Legal/Data, but most time its ok to leave it as is.

    This generated LUT will compress all tonal and color information without any clipping.

    in Resolve:

    - add color space transform node to timeline and set input: as timeline and output matched to input in your generated LUT.
    - add one more node with LUT.

    Adjust image with contrast + pivot sliders in the node located before LUT. This way you will get a reach colors and contrast but never get a clipping and ugly video look.

    One more useful trick with LOG footage is that you can mimic Exposure(ISO) RAW slider with gain slider.
    - add color transform node: timeline to linear
    - add one more color transform node: linear to timeline gamma.
    - adjust gain in first node (this will act same as expose/iso)

    Remember that when your image in LOG mode the tools works in different way.

    here are also two articles that helps to understand Sony vs Arri color/gamma compression methods and LUTCalc settings.
    http://www.provideocoalition.com/hac...ony-f-cameras/
    http://www.provideocoalition.com/lut...us-a-free-lut/
    Great tips! I tried the LUTcalc with these parameters:

    Rec Gamma - BMD Film 4.6k
    Rec. Gamut - Blackmagic Passtrough
    Out Gamma - Amira 709
    Out Gamut - LC709

    Before the LUT, I created the color transform node with the following:

    Both inputs : as timeline
    Output Gamma: Amira709
    Output Gamut: L709

    I'm getting a slightly more pinkish image than I usually do, but it's definitly softer on the highlights then the BMD LUT. Seems to retain more information. Do you know if it's better to use different parameters?

    Thanks
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  10. #10  
    Senior Member david evans's Avatar
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    Out of curiosity, I decided to try a grade in both color spaces, just to see the differences. First thing I noticed is that ACES blows out a lot more and brings a reddish tone to the image. Once that's corrected, everything looks natural (you can actually see the difference in the blue color of the coats. Skin tones seem to match, but blue is very different). I had to boost saturation a bit and do a lumma curve in ACES grade, though. In YRGB grade, I merely threw in the BMD 4.6k V3 LUT and adjusted levels in prior node.

    Here are my attempts. What do you think?


    ACES

    pai - Aces v6_3.1.7_3.1.8.jpg


    YRGB

    Pai - RGB_3.1.2.jpg
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