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    #31
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    Quote Originally Posted by visceralpsyche View Post
    Set your zebras to 80% IRE in the case of the GH5's V-Log implementation, and you will accurately know where the exact clipping point is. Stop down until those zebras just disappear. Voila. ETTR done
    Only if you don't care about the color fidelity of your brightest objects!

    If you were to try that technique on a shot where caucasian skin is the brightest object in the scene (a dark-haired person in a dark scene perhaps) you'll probably find that your skin tones have shifted all to yellow. 80 IRE on VLOG-L is absolute clip -- it's higher, relatively, than 105 zebras are on a normal gamma.

    Remember that the IRE is a cumulative formula, made from the individual brightness of the R, G, and B channels. If an object is primarily red or primarily blue, then that red or color channel stands a very high prospect of being clipped when the IRE brightness is that high.

    Your technique would probably work better if you set the zebras to 75, so at least whatever the hottest object is has a prayer of not having at least one if not two color channels clipped.


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    #32
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    Quote Originally Posted by joe12south View Post
    I think what he is saying is that he uses a grey card under the same lighting as the subject. Expose for that known value and the skin will be where it is supposed to be. If I misunderstood, please correct.
    Yup, got that part. I'm more curious about actual values and ranges when using false color and zebras for the grey card, and specifically how to approach that with Vlog as opposed to a standard profile.

    ETTR has you basically just worrying about the brightest part of the image, but the other approach has you using zebras for a grey card/white card and false color as well...I'm assuming?


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    #33
    Senior Member visceralpsyche's Avatar
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    Quote Originally Posted by Barry_Green View Post
    Only if you don't care about the color fidelity of your brightest objects!

    If you were to try that technique on a shot where caucasian skin is the brightest object in the scene (a dark-haired person in a dark scene perhaps) you'll probably find that your skin tones have shifted all to yellow. 80 IRE on VLOG-L is absolute clip -- it's higher, relatively, than 105 zebras are on a normal gamma.

    Remember that the IRE is a cumulative formula, made from the individual brightness of the R, G, and B channels. If an object is primarily red or primarily blue, then that red or color channel stands a very high prospect of being clipped when the IRE brightness is that high.

    Your technique would probably work better if you set the zebras to 75, so at least whatever the hottest object is has a prayer of not having at least one if not two color channels clipped.
    Yes, this is a fair comment I've often thought about using 75% IRE as my suggested clipping point for V-Log. In fact I recommend something similar for my Cine-D settings on the GH5, using 100% IRE as the zebra point to give a bit of headroom for saturated bright colours, for the same reason.

    I think I might recommend 75% IRE for my V-Log settings to give a similar amount of headroom, since not everyone is aware of the skintone issue at near clipping.

    Cheers,

    Paul
    Paul Leeming
    Writer/Director/Cinematographer/Actor
    Visceral Psyche Films
    www.visceralpsyche.com
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    Mobile NL: +31 6 2095 2590
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    #34
    Senior Member wschmid's Avatar
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    To the question of the base iso... what do you find in the net? A lot of statements - most see the base iso for both the GH4 and the GH5 at ISO 400.


    The GH4 native ISO is 800 according to Panasonic. It’s definitely the best option when shooting V-log. I think a native ISO of 400-640 would be more appropriate for 4K in the other picture settings.
    http://www.mkeproductionrental.com/g...o-tips-tricks/

    The base ISO for VLog-L is ISO 400.
    http://cheesycam.com/panasonic-gh4-v...ore-and-after/

    While using the V-Log L profile the new base ISO is 400, not 200, so make sure to bring some ND filters along of you are shooting daytime exteriors.
    https://www.eduardoangel.com/2015/09...vlog-tutorial/

    Panasonic GH4 has ISO 400 in V Log L
    http://www.4kshooters.net/2015/06/19...nic-g7-review/

    Nick states that the GH4 VLOG L base ISO is 400 and 800 looks great
    http://eriknaso.com/2015/07/08/gh4-v...wood-for-clip/

    As a result, the GH5’s base ISO is 800 (a figure misattributed to the GH4 in an interview with one of Panasonic’s Japanese executives).
    https://suggestionofmotion.com/blog/...panasonic-gh5/

    Bemerkungen zur Base ISO 400

    Die Base-ISO der Kamera liegt in V-Log bei 400. Diese Erkenntnis fällt bei der GH5 besonders leicht, da die Kamera auch mit Gain-Werten arbeiten kann und 0 db Gain exakt den 400 ISO entspricht. Interessant ist dabei vor allem, dass dies auch in den anderen Bildprofilen gilt, in denen man auch Einstellungen unter ISO 400 findet.

    Ein kurzer Check bestätigte: ISO 400 entspricht auch im Standard-Profil weiterhin 0dB, während ISO 200 mit -6dB angegeben werden. ISO 200 entspricht also einem Negativ-Gain und somit einer Absenkung unter die Base-ISO, zumindest wenn die angezeigten Zahlen stimmen sollten (wovon wir stark ausgehen). Und das würde wiederum bedeuten, dass man auch in den anderen Profilen für die beste Dynamik immer ISO 400 wählen sollte, selbst wenn ISO 200 vorhanden ist. Und es ist stark anzunehmen, dass dies auch für den Fotobereich zutrifft. Diesen Beweis überlassen wir aber den einschlägigen Foto-Test-Gazetten…
    https://www.slashcam.de/artikel/Test...e-I.html#Bemer
    Kind regards,

    Wolfgang


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    #35
    Senior Member Thomas Smet's Avatar
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    That is because it is the base ISO. Base ISO is not native ISO. Base just means the lowest it can go. You can only go down to ISO400 if you shoot V-log. That is how it was designed and a fact of the camera. It isn't some belief of the internet but a cold hard fact. Those articles are pointing out that V-log does start at ISO400 just like the Sony starts at ISO1600 when shooting log. It isn't an assumption of what is the native ISO but the only way you can shoot log at the lowest allowed ISO level. Some people have assumed the GH4 has a native ISO of 400 because of V-log but that is just a guess. Base just means base.


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    #36
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    Question about proper exposure for GH4 and GH5 V-log using an external waveform monitor.
    Do you expose for 42 ire while monitoring with the V-log to 709 lut active?


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    #37
    Senior Member Bern Caughey's Avatar
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    Entirely depends on whether the Waveform represents the underlying LOG, or the LUT.


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    #38
    Senior Member Cary Knoop's Avatar
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    Quote Originally Posted by conraddmb118 View Post
    Hey all,

    I've been searching around for an answer to this, but I was wondering if anyone could shed light on the proper exposure for V Log on the GH5. I used V Log on the GH4 and remember that stopping up 1-2 generally provided better results than 0. Is this true for the GH5, too? I have not been able to get my hands on another copy of V Log yet, so I am unable to do any tests.
    Just expose right, not under and not over, this will give you the best picture.

    The only exception I am willing to take is in case there is too little light, in that case there is not much of an alternative to over expose the video.


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    #39
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    Just expose right, not under and not over, this will give you the best picture.
    We're always looking for tricks...some hidden knowledge beyond the obvious...that is going to change the fundamental reality that these cameras have little room for exposure error. I've spent so much time and effort over the years chasing a magic bullet, starting over with each new camera, ultimately to come back to this basic truth: light for your subject, expose for that light, then do what you can to control the rest of the scene.

    And that's just for a baseline, "technically" correct exposure. But the exposure you really want is the one that helps tell your story. Here's a still from a recent screen test:



    Look at that histogram out of context, and that's a bad exposure. Look at that histogram in the context of the story, and that's exactly the right exposure.


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    #40
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    right exposure is your right exposure
    gh5 when you read in DB instead of Iso, you can see that 400 iso is 0 db, that mean is native sensibility of that camera, not gain more or less...
    different style of shooting, different contrast of picture, different right way to exposure. You can use false color to check that is right exposure on some part of picture, if you want, but is not a right science.
    i think to a Andrew laszlo that volontary underexpose a film when shoot Rambo (first blood), to force later in developing to have a picture more hard like war documentary...
    We have tool to choose right exposure, then we can create more with light...


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