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    Exposing for HLG
    #1
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    Hi all,
    When you are exposing for HLG, is it correct to say that you want to ETTR?

    The two tutorial I can find address it are here:
    https://www.youtube.com/watch?time_c...&v=vX8_zect8ag
    and here:

    In the first vid, he suggests putting zebras at 95%, then just dialing down until nothing is clipping except for bright lights and the sun.


    In the second, he suggests setting the clipping point at 90% and ETTR.
    https://www.leeminglutpro.com/downlo..._Panasonic.pdf

    Does everyone agree that's pretty much the best way to expose for HLG?

    Is it better to do that versus exposing to middle gray?

    I always thought that exposing to 18% gray or 90% white would give more consistent results than ETTR.

    Thank you!!
    Last edited by karma17; 11-05-2019 at 07:25 PM.


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    #2
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    Unlike V-Log-L, HLG shadows are really clean, so you don't have to try and squish the images to the far right side, as you'll undoubtedly lose the highlight detail the picture profile was designed to retain.

    I use my Ninja V to give me a decent HDR view of the scene to help set exposure. And last but not least is the waveform monitors, as long as you know where they can go safely.


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    #3
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    This document from the ITU suggests that for HLG an 18% gray card should be about 38 IRE on a waveform monitor and a 90% reflectance white card should be about 73 IRE:
    https://www.itu.int/dms_pub/itu-r/op...2017-PDF-E.pdf


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    #4
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    Thanks so much!! This is just what I was looking for! That article is very helpful!!! I got in the habit of using a 90% white card when I had my FS7, and usually, I got consistent results that way. I expose V-Log at 61% IRE and so I can see now that HLG goes to 73 at 90%. I was shooting some test footage today and it seemed my HLG was under exposed the way I was doing it. Thanks again.
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    #5
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    Since I posted this, I've been researching this quite a bit, and have concluded that ETTR is probably the best approach to expose HLG.
    Art Adams has an excellent piece here:
    https://www.provideocoalition.com/a-...1-what-is-hdr/
    and after reading that and connecting the dots with the GH5 having Mode 1 and 2 in Assist View, I figure that Adams is right about the need to protect the highlights at the expense of underexposing shadows.

    But he also clarifies that you need to light your subject or get light on your subject if bringing down the highlights makes the shadows completely pitch black. And I guess it all makes sense because HDR and HLG are all about the range and getting as much of the range as you can, and that's not happening if highlights are getting clipped.

    Any way, that's my understanding of it now.


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    #6
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    Quote Originally Posted by karma17 View Post
    Since I posted this, I've been researching this quite a bit, and have concluded that ETTR is probably the best approach to expose HLG.
    Art Adams has an excellent piece here:
    https://www.provideocoalition.com/a-...1-what-is-hdr/
    and after reading that and connecting the dots with the GH5 having Mode 1 and 2 in Assist View, I figure that Adams is right about the need to protect the highlights at the expense of underexposing shadows.

    But he also clarifies that you need to light your subject or get light on your subject if bringing down the highlights makes the shadows completely pitch black. And I guess it all makes sense because HDR and HLG are all about the range and getting as much of the range as you can, and that's not happening if highlights are getting clipped.

    Any way, that's my understanding of it now.
    No, you had it correct before you changed to this. ETTR is bad idea for any log and especially HLG which is 17.5 stops DR while camera is only 11-12. It is true that HLG is easy to overexpose, but because the gamma is spread over so many stops, any individual stop has many fewer data points than 709 gamma, so it's incumbent to expose the important subject matter where the data is. That's usually middle gray. If it's landscape and you really want to protect highlights then okay protect them. But if it's models and skin, then expose that for the middle and let the highlights fend for themselves. Zebras can be a tool here. The key difference between using a tool like zebras and ettr is that the latter is always changing, never the same. You'll have to cc every scene because the middle gray exposure is never the same. Zebras are a fixed reference point in the curve.


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