Thread: Exposure post or pre LUT - Whats your workflow?

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  1. #1 Exposure post or pre LUT - Whats your workflow? 
    Hey people,

    how do you like to expose the image with in camera or monitor tools?
    Pre LUT or post LUT?
    My Video Assist measures exposure pre LUT and I dislike that.
    I would love to be able to judge exposure of off the manipulated image to firstly drop my LUTs in Resolve onto the footage and have it exactly like I shot it on the day (so I exactly controll my black and white points) and also to be able to use easily use LUTs that handle +1 or +2 exposure for me.
    Its one of the biggest drawbacks of my BM VA and actually a reason for me to upgrade to a SmallHD or similar.
    Also I am under the impression that I can not be 100% sure that I have saved my highlights, or am I getting that wrong?

    What are your thoughts?
    How do you do it?
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  2. #2  
    I much prefer my tools measuring pre-lut, since I'll know if I'm actually clipping any whites or blacks (as opposed to the LUT saying information is gone even when it isn't). Having a LUT convolute my exposure tools would trick me into underexposing a little since I prefer to ETTR. I do monitor everything with a LUT on, though. If you want it to measure it post LUT, make sure that you're sending a video signal to the VA with a LUT on it. Not sure what camera you're using, but I can do this easily with the Ursa Mini Pro. So you need to put the LUT on the video signal before it gets to the VA instead of applying the LUT in the VA once it gets the clean feed. I don't own the VA, though, so I apologize if it isn't as easy as the way I'm making it sound.

    Edit: this would then result in only recording the baked in LUT image if you're recording to the VA. Not sure if that would be a problem for you.
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  3. #3  
    Senior Member TeddyDem's Avatar
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    Quote Originally Posted by Rotbart View Post
    Hey people,

    how do you like to expose the image with in camera or monitor tools?
    Pre LUT or post LUT?
    My Video Assist measures exposure pre LUT and I dislike that.
    I would love to be able to judge exposure of off the manipulated image to firstly drop my LUTs in Resolve onto the footage and have it exactly like I shot it on the day (so I exactly controll my black and white points) and also to be able to use easily use LUTs that handle +1 or +2 exposure for me.
    Its one of the biggest drawbacks of my BM VA and actually a reason for me to upgrade to a SmallHD or similar.
    Also I am under the impression that I can not be 100% sure that I have saved my highlights, or am I getting that wrong?

    What are your thoughts?
    How do you do it?
    The SmallHD monitor (500 and 700 series) exposure tools are also pre-LUT.
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  4. #4  
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    Exposing your image for a canned LUT is back asswards. If properly exposed footage looks bad then you need to tweak the LUT and re-export it and use that instead. Not all cameras are going delegate the same amount of stops over and under middle grey, a canned LUT can't compensate for this. Depending on the LUT and how you shoot it may simply require changing the ISO in camera.

    If you always shoot 1-2 stops over then adjust the LUT accordingly, or shoot ISO 200 or 400, but any LUT that has that much headroom over baseline exposure is going to be relatively flat and loggish. Shooting log the Micro/Pocket/BMCC have about 5 over and 8 under, Rec709 has about 3 stops over mid grey, which is what most in-camera/monitoring LUTs are adjusting for. If you want a LUT that's going to give you 2 stops over you'll have to use one that doesn't doesn't eat very far into the contrast curve.
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  5. #5  
    Senior Member rick.lang's Avatar
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    For what it's worth, I tried using the default BMD Video LUT on the URSA Mini 4.6K (firmware 4.3.1 at the time), and I hated what it did to my falso colour which I s my primary exposure tool. It showed me lots of yellow and red areas. Turned off the use of the LUT, and not a pixel was above light grey. Please don't expose with in-camera LUTs in general. They're meant for the Director's monitor feeding from the 12G SDI to evaluate what the video might look like in post. As a camera operator, you want to see all the dynamic range nuances in Film mode. Only possible exception I can think of: recording in ProRes and handing off footage to someone who requested you to do that.
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  6. #6  
    Senior Member CaptainHook's Avatar
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    Quote Originally Posted by rick.lang View Post
    For what it's worth, I tried using the default BMD Video LUT on the URSA Mini 4.6K (firmware 4.3.1 at the time), and I hated what it did to my falso colour which I s my primary exposure tool.
    Display LUTs don't affect false colour, do you mean you changed from Film to Video in the record settings?
    Blackmagic Design
    My BMD LUTs.

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