╬ HDR to 8 bit Vegas Grading Tip ~~ Reclaiming the Shadows ╬

Musicvid wrote on 11/10/2019, 3:59 PM

╬ HDR to 8 bit Grading Tip ~ Reclaiming the Shadows ╬

Content courtesy Gordon Laing / Cameralabs

  • When rendering 8 bit videos from HDR / 32 bit float projects in Vegas, a narrow band of monochrome quantization noise appears to take over the bottom 5% of RGB color space.

Source: GH5 10 bit 422 Project: 32 bit Float, Video Levels.

8 bit output pipeline

  • Spoiler: To skip the tl;dr part, here is the solution to remove the unwanted noise from your 8 bit renders:

Apply the Levels filter to your 32 bit project as such:

  • Before:

  • After:

  • Side by Side:

If we isolate only the added noise by a 10:1 factor, we see from the histogram that it is spurious narrow negative sideband monochrome noise, unrelated to the original 10 bit image integrity. So much for Hogwarts' School of Grading.

  • What did we do? We added a nondestructive low block filter, to isolate and precisely remove some unwanted frequencies from the video.
  • How did the noise get there? This is the kind of spurious sideband noise that would normally get clipped out of gamut using good integer leveling techniques. In a float project, it sits right alongside the lowest program bits, and lacking fixed endpoints, will be imported right along to the compressed 8 bit space, unless excised first using a technique such as this.
  • Conclusion: When rendering 8 bit video from HDR / 32 bit float projects, shadow noise can be reduced and apparent sharpness increased by applying a 0.05 to 0.10 Shadow Mask, using the Levels plugin.
  • When rendering from 8 bit projects, regardless of source, there are no differences, and no apparent correction is needed.

In this example, a low cut at 0.088 separated the noise from the signal, preserving the detail while cleaning the shadows.







Musicvid wrote on 2/15/2020, 3:41 PM

Other dithering examples here.


Reyfox wrote on 3/5/2020, 6:57 AM

Is that Gordon narrating?