Thread: Pocket 4K red clipping

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  1. #21  
    The problem is much less visible with others cameras, as we can see with Ryanite screenshots, even in V4 colour science. It affects only the red channel. And the fact that it can be manageable in resolve (with counterparts) shows that you can't use others NLEs. That is why I think that it's not just a common exposure problem. It's a BMPCC4K problem.
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  2. #22  
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    Here is a screen shot with scopes of the extended video gamma segment. Straight REC709 to the timeline as in your original settings. You can see the hard clipping in both RGB parade and vectorscope. The arrows pointing to white lines on the RGB scope graticule indicate REC709 reference white at 940 and reference black at 64.
    Try some similar experimental shots and bracket your exposures +2 to -2 in 1/2 stop increments to get a better idea of what works. Shoot at the camera's native 800 ISO setting.
    Shoot some short raw clips too. Prores is just video.

    BMPCC4k 709 over.jpg
    Last edited by razz16mm; 10-19-2018 at 07:29 PM.
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  3. #23  
    It is not an overexposure issue. Yellows, blues, greens are perfectly handled when overexposed : desaturated with a creamy hallo around. The reds are oversaturated with harsh boundaries, like it was digitally painted.
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  4. #24  
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    Quote Originally Posted by razz16mm View Post
    Here is a screen shot with scopes of the extended video gamma segment. Straight REC709 to the timeline as in your original settings. You can see the hard clipping in both RGB parade and vectorscope. The arrows pointing to white lines on the RGB scope graticule indicate REC709 reference white at 940 and reference black at 64.
    Try some similar experimental shots and bracket your exposures +2 to -2 in 1/2 stop increments to get a better idea of what works. Shoot at the camera's native 800 ISO setting.
    Shoot some short raw clips too. Prores is just video.
    Attachment 26956
    ehh how is prores "just video" prores can handle a very similar amount of dynamic range, shoot in film log and with the prores codec should not create this effect.
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  5. #25  
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    Quote Originally Posted by Ryanite View Post
    ehh how is prores "just video" prores can handle a very similar amount of dynamic range, shoot in film log and with the prores codec should not create this effect.
    Log curves compress sensor linear DR into smaller display DR color spaces. They allow you to preserve values and details that would otherwise be clipped and lost. Prores 10 bit 4:2:2 is pretty much a standard REC709 compliant video codec.
    Either way, even the sensor has its limits. What you are seeing is strictly the result of exposure produced hard clipping as the scopes clearly show, both in log and in REC709. It is baked in in Prores and you don't have any recovery room.
    Linear raw file DR is only limited by the camera sensor. Not so with Prores in any of its forms. But the sensor is clipped here too it looks like.
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  6. #26  
    Senior Member Frank Glencairn's Avatar
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    If it is clipped, it's clipped - period.

    You can do some sort of highlight recovery, but that's just a band aid - just don't clip it.
    Raw gives you a bit more wiggle room though.

    Having said that, aggressive monocromic LEDs can be a problem on any camera, no matter what color.
    But since we don't have blue brake lights or traffic lights, the problem shows up mostly with red.
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  7. #27  
    There are two points I wish to answer.

    First, when it is clipped with a BMPCC, it doesn't react the same way than with a BMPCC4K. Actually, it reacts a much better way as you can see in those exemples taken from raw files, same night and same optical setup :

    BMPCC raw v1_1.1.1.jpg
    BMPCC raw v4_1.1.2.jpg
    BMPCC4K raw _1.2.1.jpg
    Attached Images
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  8. #28  
    Second, the issue is only concerning the RED lights. No problem with the greens or the yellows.
    You can correct it by using the color transform tool and the saturation mapping. But it affects the entire image, including the skin tones.

    BMPCC4K prores ev_1.3.4.jpg
    BMPCC4K prores corre ev_1.3.3.jpg
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  9. #29  
    Senior Member shijan's Avatar
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    New camera always means new problems and risks. It's always like to be a beta tester. Best scenario is that BM team will fix it in firmware. Worst scenario is send it back to factory to recalibrate sensor. (Do you remember Pocket v1 "white orbs" problem?) My guess it is something wrong with Color Science v4 and it should be reported to developers and fixed.

    Don't you interested to share those side by side BMPCC v1 vs P4K DNG samples? Or some other samples with light bulbs in the dark to compare dynamic range/noise limits?

    BTW i found that old thread "Ursa Mini 4.6k Blue LED light looks Magenta" https://forum.blackmagicdesign.com/v...ic.php?t=54377 if you download DNG you can see similar problem with wired single color clipping.
    Last edited by shijan; 10-19-2018 at 10:04 AM.
    All my custom made accessories for BMMCC/BMMSC now available here https://lavky.com/radioproektor/
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  10. #30  
    You can find prores and dng in this link :
    https://www.dropbox.com/sh/d6p9k043v...h43D4Aw-a?dl=0
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