Thread: Ursa Mini Pro - Film log curve is not that flat

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  1. #1 Ursa Mini Pro - Film log curve is not that flat 
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    (My english is not the best...sorry)

    I've been testing my new camera UMP 4.6K for about a month...Got lot of wonderful cinematic images, texture, colors. But there's something interesting about the film log curve.

    I've seen in other posts and videos showing that the UMP LOG Curve is not as flat as the BMD Film log (which i love a lot) used to be, or even the 4.6K Film Log.

    The UMP highlights values are higher than it's predecesors, so when you apply the in camera 4.6K Film to REC 709 lut, you get extremely clipped highlights even if you underexpose your scene . The contrast you get is really high. Same thing happens when you apply even the 4.6k to REC709 V3 LUT inside Resolve. BMD says the new log curve have been designed for an easier grade. So my question is...

    1) Why BMD have not realeased an official UMP Film to REC709? cause im pretty sure those Luts are not for UMP. And yes, We all know you can create your custom Luts, but it would be better having the official lut from the manufacturer. Just saying..
    2) Have you experienced this situattion too?
    3) Would be wonderful having a log curve as flat as before...just my personal taste


    Anyway, I love my camera a lot...just had a doubt about it...

    BTW, this video is about 4.6k vs PRO and says something about this too ... https://www.youtube.com/watch?v=D7x80ehtPgY&t=
    Last edited by ravfx; 01-22-2018 at 04:45 AM.
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  2. #2  
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    Yeah I dont use that REC709 LUT because of this.

    https://www.youtube.com/watch?v=T31lBQymEPs
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  3. #3  
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    why does how 'flat' the log curve is matter if it encodes all the dynamic range the sensor is able to get anyway?

    I never understood this equation of 'flat' with range - its the opposite in fact . Given limited bit depth the flatter the image is, the less of the full range of the image depth you are using. The ONLY point of 'flatness' is to make sure the image maintains highlight data...

    the LUT issue I entirely understand though - I agree camera manufacturers should make available the 'reference' transform into rec709 and it seems here the current LUT hasn't really been updated with the latest UMP film profile in mind
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  4. #4  
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    Stelvis, you are right, I'm still learning a lot about this Log thing...I'll keep working on my new workflow for this camera, and it would be awesome to have an official UMP film to REC709 LUT so I can show a better image to my client while we are on set.
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  5. #5  
    Senior Member CaptainHook's Avatar
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    The URSA Mini Pro uses the same Log curves as the URSA Mini 4.6K which are "flatter" than the original BMD Film.
    Blackmagic Design
    My BMD LUTs.

    **Any post by me prior to Aug 2014 was before i started working for Blackmagic**
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  6. #6  
    Senior Member shijan's Avatar
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    It is better to forget those factory LUTs and use Color Space Transform node with Luminance and Saturation mapping turned ON.

    To generate LUT from Color Space Transform node transformation you need to use trim_lut0.dpx file that ships with Resolve. There is known tutorial about how to use it https://www.elephorm.com/etalonnage-...ction-primaire

    - In project settings set Timeline to BMDfilm or whatever your footage is.
    - Input and output color spaces set to Bypass.
    - Put trim_lut0.dpx file to timeline.
    - Add Color Space Transform node with Luminance and Saturation mapping turned ON.
    - Save result to LUT file to use outside Davinci Resolve.
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  7. #7  
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    Quote Originally Posted by shijan View Post
    It is better to forget those factory LUTs and use Color Space Transform node with Luminance and Saturation mapping turned ON. .
    Very interesting! I was watching a tutorial from Juan Melara covering that technique, I still have lot of things to learn, I'll keep exploring more. Thanks a lot for the support!
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  8. #8  
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    Quote Originally Posted by shijan View Post
    It is better to forget those factory LUTs and use Color Space Transform node with Luminance and Saturation mapping turned ON.
    the OP's basic point was more that the factory rec709 LUT for the UMP seems overly contrasty and clips too easily - ones from say Arri for the alexa seem to be more finely judged.

    I Don't think anyone would argue that any of these sorts of 'quick' LUTS are the last word in achieving the best final image, more how useful they are as a reference point
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  9. #9  
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    Quote Originally Posted by Stelvis View Post
    the OP's basic point was more that the factory rec709 LUT for the UMP seems overly contrasty and clips too easily - ones from say Arri for the alexa seem to be more finely judged.

    I Don't think anyone would argue that any of these sorts of 'quick' LUTS are the last word in achieving the best final image, more how useful they are as a reference point
    Its even completely useless as a reference point.
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  10. #10  
    Senior Member CaptainHook's Avatar
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    Our supplied Video LUTs are basically 709 gamma and are there for broadcast type users - which is not a useless reference point. Being "overly contrasty" and "clipping to easily" is how the standard defines the Rec.709 gamma.
    Blackmagic Design
    My BMD LUTs.

    **Any post by me prior to Aug 2014 was before i started working for Blackmagic**
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