Custom lens flares creating "bands" on footage?

HeySiri
HeySiri Posts: 386 Just Starting Out*

I imported this shot I made from Blender—the footage was rendered with 16 bits color depth and I confirmed it retained that bit-depth after transcoding to ProRes 422. In Hitfilm, I set my workspace to 16-bit as well, but when I add the Custom Lens Flares effect to a grade layer, I get these "bands" over my footage. The bands are less noticeable at 16 bits than 8 bits—could it just be my monitor not being able to show enough colors for a smooth transition?

Regardless, this is just for a personal project so the bands aren't a huge issue—but if there's a simple solution, I wanted to check. Thanks!


Answers

  • NormanPCN
    NormanPCN Posts: 4,298 Expert

    Prores standard and HQ are 10-bit codecs, which should be fine from Blender. Prores XQ can do 12-bit. Of course, 16-bit float is actually a 10-bit mantissa.

    What are we looking at here?

    • Screenshot from the Hitfilm viewer?
    • Exported frame from Hitfilm (to PNG it seems)
    • ???

    Assuming an export frame from Hitfilm.

    The second shot with the highlighted area is a PNG which will be 8-bit. Anything 8-bit can have problems with gradients in the very dark areas. Just not a lot of bits on the lower end of things (dark(er) areas). I not done anything like that (quite so faint and dark). I have done glows, into black space, and needed a 16-bit float timeline to get that smooth. It did look fine and exported to 8-bit AVC okay with enough bitrate.

    If your Hitfilm viewer, at 100%, has the bands, then that is the truest result. If you can tell us what lens flare you have here, it settings, and the background color or whatever, then that is something that seem easy for us to try and reproduce on our machines.

  • NormanPCN
    NormanPCN Posts: 4,298 Expert

    I just tried the Batman flare, and I see banding in the viewer over the plain black background.

    Again, to a part of your question. Is it my monitor? Can't say. My monitor is kinda sorta able to accept 10-bit output but next to no software supports that (or properly supports). Sure as heck fire not anything here.

    I don't know what precision the Hitfilm gradient generator, that lens flare uses, operates at. Hopefully not always 8-bit.

  • HeySiri
    HeySiri Posts: 386 Just Starting Out*

    In my post that was an exported frame from Hitfilm—but when I exported it to ProRes it still showed the banding. I have access to a better monitor at work, so I'll try it out there on Monday to see if it's a monitor issue or something in Hitfilm itself.

  • NormanPCN
    NormanPCN Posts: 4,298 Expert

    Better monitor is something to question what better means. Just better at rendering the 8-bit signal or a true 10-bit monitor receiving a true 10-bit signal. Very little software supports true 10-bit monitors, let alone 8-bit + FRC.

    I've been thinking there is more here. In the past I have done some glows on space like scenes. So black background and the glow has a gradient falloff. My monitor and Hitfilm are certainly 8-bit displayed. My monitor is technically 8-bit + FRC capable but I don't try to mess with that.

    So with the glows I have seen banding with the Hitfilm timeline render at 8-bit. Switching to 16-bit timeline then things got smooth. Well, output is still displayed 8-bit. 8-bit AVC output as well. So 8-bit seems it was capable of a good gradient in those instances. Hitfilm generated gradients simply were not on a pure 8-bit timeline.

    Now your example, and my quick test, have very long and thus very gradual gradient falloff. My glows fell off quicker. Over shorter distance. They were also brighter over much of that distance. Also, that was Glow which is, or probably is, different than whatever the flare code uses. Things we cannot know or test.

    I general it is probably best to try and avoid very long falloff, in very dark areas, on such things.

  • HeySiri
    HeySiri Posts: 386 Just Starting Out*

    @NormanPCN Sorry for the late reply, life got busy. The issue was less visible on my monitor at work, but still present. Turning down the brightness of the flare glow (essentially limiting the falloff) took away a lot of that banding, so that's a fix for now.