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Strange Pattern in RAW frames

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  • Strange Pattern in RAW frames

    I was looking at some footage I shot the other day, and there seems to be a slight "grid" pattern in the image. When I open up an individual RAW frame in Photoshop, I do not see this pattern at 100%. If I grade and output the footage from Resolve, I do see it on playback. I've set Resolve to scale and debayer at the highest quality. Just FYI I was outputting the 4k RAW as 4K DCI scope, so there was a very slight upscale. I'm playing it back on a 30" monitor, which isn't 4k resolution, so it will be downscaling it on playback. I haven't found a way to play it at 100% scaling.

    As I don't see it in the individual frames, I'm thinking it's a scaling issue in either Resolve, or on playback on my Mac.

    Has anyone else experienced this?

    (grid pattern visibly in top right of frame, to the left of the flare)

    edit: attached image removed, looks like the forum has scaled this screen-grab, here is a link to the original grab - https://www.dropbox.com/s/5tz6vzxhru...ddity.jpg?dl=0
    Attached Files
    Last edited by DJJ; 06-21-2015, 12:21 PM.

  • #2
    Not seeing it.

    Does your monitor have burn-in issues (image persistence)?

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    • #3
      Originally posted by André View Post
      Not seeing it.

      Does your monitor have burn-in issues (image persistence)?
      You can't see it in the forum post image, you'll probably need to look at the screenshot.

      No on the monitor front, it's a very good monitor (NEC SpectraView Reference 301).

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      • #4
        100% crop from the screen grab, showing the pattern.

        4k-raw-oddity-02.jpg

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        • #5
          Wow. I can see it now.
          And this was totally NOT there when you looked at the RAW images?
          For info gathering purposes, have you tried taking just one random RAW frame and processing it in either PhotoShop or Resolve, or both?

          In other words, if it's not there in the original RAW, can we determine at exactly what stage does the pattern show up?
          Cameras: Blackmagic Cinema Camera, Blackmagic Pocket Camera (x2), Panasonic GH2 (x2), Sony RX100 ii, Canon 6D, Canon T2i,
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          • #6
            Ok, I've done some more testing, and it looks like this pattern is an aberation of the real-time scaling on MacOS-X (latest Yosemite 10.10.3). When you preview or play an image that's too big for the screen, it will be rescaled, and in this instance, it is causing this issue.

            I've taken a single frame and processed it in Resolve, and again in Photoshop, and exported. Looking at either in preview shows this pattern (the Photoshop one was worse). Looking at the Resolve image at 100% (in Photoshop) the pattern is not present. Panic over

            Looks like the issue is down to the OS or gfx card drivers. Sorry for the false alarm, useful though if anyone else has this trouble.

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            • #7
              Resolve debayer can produce "zipper" artifact patterns too depending on the codec you export to.

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              • #8
                I've had resolve create patterns like this in the preview window at certain scales, sometimes even moire. Once it's rendered out, it's fine.
                I think they just cut some corners for the sake of playback speed.
                "Senior Member"???... Really???...
                Not to be taken seriously...by anyone.....

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                • #9
                  Specifically, it's not Resolve where I see this, it's in the rendered footage viewed outside Resolve. The fact I saw it in "Preview", Quicktime and VLC initially suggested to me it was baked into the footage, which was the cause of my concern.

                  The testing showed this not to be the case, and it's caused by the OS-X realtime scaling, so it's either down to their gfx API or the gfx card drivers.

                  Proven by loading a single frame to both Photoshop and Resolve, and not seeing the pattern at 100%. Further loading of the Resolve processed frame into Photoshop to view at 100% shows no pattern. And "viewing" either still frame or footage outside of those packages, the OS will scale it to fit my screen and I see the pattern (on both Resolve and Photoshop sourced images).

                  Curiously it's just one part of this image where it's apparent, not the whole image, and so I'm guessing there's some pattern frequency in that area which doesn't play nicely with the scaling algorithm.

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                  • #10
                    This is kind of related to the famous "grid" patterns that used to plague the BM cameras (and sony cameras)

                    It's related to scaling and playing back at different resolutions to the origination resolution.

                    it has always gone away once rendered footage is rendered to a standard size like 1920 or one of the 4K standards...

                    You can sometimes induce it if you render out to non standard sizes, but as I say, it's more likely a scaling related issue in playback.

                    JB

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