Click here to go to the first RED TEAM post in this thread.   Thread: Return of Purple Fringing.

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  1. #21  
    Senior Member rand thompson's Avatar
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    Rick,

    I believe the non-removable OLPF on the Komodo is based on the removable "Skintone Highlight" OLPF on other DSMC2 Red cameras, someone correct me if I'm wrong. Maybe there's some Sensor/OLPF/Color Science interaction anomaly causing this also. Or maybe a Lens Coating/Sensor/OLPF issue.
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  #22  
    Two types of CA we normally see: axial and radial. This is axial. How do you tell them apart? Radial is least in the centre of the image and increases toward the edge of the image, and the colour fringes will be on the inner / outer edges. Axial is quite different - you'll get different colour fringes depending on if the object is in front (purple) or behind (green) the plane of focus. Axial CA is reduced by stopping down the lens. It is made more visible from the contrast of the edge. There's a theory posted on wikipedia on this CA that's it's some kind of sensor blooming from over-exposure and pixels spilling over into neighbours. I first tested that theory back with Red One when I first really noticed this kind of CA - and that theory is not the explanation. I tested it thoroughly and it's purely lens - not sensor blooming. Once we saw it we popped the lens onto our Canon DSLRs and guess what - same CA there.

    Then I started noticing it in old films shot on film - you can clearly see it in the headlights of the cars in The Fury, for instance. Now I see it everywhere. What has changed is we have higher resolution cleaner sensors that don't hide this kind of thing, and the easy ability to pixel-peep.

    Graeme
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  3. #23  
    Senior Member rand thompson's Avatar
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    Thanks for chiming in Graeme!!
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  #24  
    Quote Originally Posted by Mike P. View Post
    Is that a hardware/sensor design change with Komodo, or a colour science/debayer/software-side change for all r3d footage?

    It's tiny change to the colorimetry tables so that it travels with the R3D and doesn't require or depend upon an SDK change - that means there's no decode compatibility issues where if you'd opened the R3D with an older SDK you'd get a slightly different image.

    It has nothing to do with CA and has no impact on CA. All that's happening is if you'd previously set the WB to 5600K, -3.26tint (as real world daylight is ever so slightly green) you'd now set it (more intuitively) to 5600, 0.0 tint. That's it. A simple change, but one that gives you an easier better starting point for your image.

    Graeme
    www.red.com - 8k Digital Cinema Camera
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  5. #25  
    Senior Member Patrick Tresch's Avatar
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    Thanks Greame, I've learned something today.
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  6. #26  
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    Thanks Greame!

    So now does anyone want to be commissioned to create me a LUT that removes neon purple for these situations :p
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  7. #27  
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    Quote Originally Posted by Graeme Nattress View Post
    It's tiny change to the colorimetry tables so that it travels with the R3D and doesn't require or depend upon an SDK change - that means there's no decode compatibility issues where if you'd opened the R3D with an older SDK you'd get a slightly different image.

    It has nothing to do with CA and has no impact on CA. All that's happening is if you'd previously set the WB to 5600K, -3.26tint (as real world daylight is ever so slightly green) you'd now set it (more intuitively) to 5600, 0.0 tint. That's it. A simple change, but one that gives you an easier better starting point for your image.

    Graeme
    Yeah I knew it was OT. Just wanted to know if it was something that'd be seen in other RED cameras (*cough*DSMC1*cough*)... I'm guessing the colorimetry tables are changeable via firmware, but this is not a big enough change to bother doing? (Does this have anything to do with the updated WB colour picker in RCXp 52.2?)


    Back on topic: While I understand these are higher res/cleaner sensors, that the CA doesn't show up nearly as much on every other camera you use the same glass with (some higher resolution than 6k) is probably quite frustrating. Best bet would be to go to a camera store and try a native RF lens. That'd get rid of a lot of potential question marks pertaining to lens performance (e.g. FD-to-EF/EF-to-RF adapting, modern lens designed for mirrorless, etc.) and allow you to decide whether it's acceptable or not for you/your work...

    Quote Originally Posted by Rick Cook View Post
    I'm more surprised others are not having the issue, which is the main reason I posted here. On most of my footage I can zoom in and find neon purple hits.
    Coincidentally, I recently heard a horror story about the Komodo facebook group deleting posts/banning people if they said anything critical of the camera (no matter how constructive). Maybe that mentality has bled over to this sub-forum and people don't want to ruin the vibe by mentioning issues/concerns they have... That said, it's just as likely no one else is having similar issues because they're not using the same adapter/lens combo. Regardless, everyone here appreciates the heads up and now Komodo users who run into similar problems will have an answer moving forward.

    Quote Originally Posted by Rick Cook View Post
    So now does anyone want to be commissioned to create me a LUT that removes neon purple for these situations :p
    Pretty sure I have Graeme's old ones. Presuming he doesn't mind, DM me your email and I can forward them over (admittedly they do remove quite a bit of purple, but they also work really well and are at least a blanket-application/set-it-and-forget-it process).
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  8. #28  
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    Quote Originally Posted by Rick Cook View Post
    I am not at home atm so can’t upload any raw clips. Here is some quick dirty footage shot with a FD 50 1.4 stopped down to F2. Again, this lens does have CA but it never glows purple like this on any other camera I have shot with ranging from DSLR’s up to MiniLF. Every lens I own is glowing like this. Maybe CA is creating out of gamut color causing it to light up like this?

    https://youtu.be/kbt9RunUtow
    I like that everybody who is speaking about some kind color casts or noise or whatever in their cameras always say that other cameras don't have it. But never take the time to shoot side be side tests. This footage says nothing, because there is nothing to compare to.
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  #29  
    Drop me an email Rick - I made some a while back and you can try them.

    Graeme
    www.red.com - 8k Digital Cinema Camera
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    IPP2, Image Processing, Colour Science and Demosaic Algorithms
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  10. #30  
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    I would like to know what lenses to use to avoid this issue. I saw many shots suffering this fringing on YouTube. Any recommodation for good and not expensive lenses for Komodo? I like Komodo' s footage but I don't like this purple and green fringing. And I wanna avoid this issue in my footage.
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