Understanding and Avoiding Blue Channel Clipping in Nikon RAW Footage with DaVinci Resolve

When working with Nikon RAW footage in DaVinci Resolve, one issue that can arise is blue channel clipping. This problem, while often overlooked, can significantly impact the quality of your final output, especially when dealing with footage that includes intense blue lighting or highly saturated blue elements. Recently, Nikon released an official workflow guide to mitigate this issue, which I had the chance to test and further investigate at NAB (National Association of Broadcasters).

Identifying the Issue

Blue channel clipping manifests as a loss of detail and color fidelity in the blue channel, leading to unnatural and unprofessional-looking footage. This problem is particularly prominent when using DaVinci Resolve’s built-in color management with automatic settings. During our tests at NAB, we found that simply using a color space transform (CST) could mitigate the issue to some extent, but the built-in color management seemed to exacerbate it.

Investigative Process

To understand the root cause of blue channel clipping, my colleague and I conducted a series of tests. We switched between different timeline color processing modes in DaVinci Resolve and noted how the footage responded. The initial findings suggested that DaVinci Resolve’s automatic color management was at fault, particularly when handling HDR and SDR timelines.

Testing Methodology

Testing Nikon RAW Footage

1. Default Settings Test:
   • Imported Nikon RAW footage directly into DaVinci Resolve.
   • Used automatic color management with HDR timeline and SDR output.
   • Observed blue channel clipping and color artifacts.
2. Custom Color Management Pipeline:
   • Input Color Space: Nikon log
   • Working Timeline Color Space: Red Wide Gamut in Log3 G10
   • Output Color Space: Rec 709
   • Exported in a 12-bit codec and re-imported into DaVinci Resolve.
   • Significant reduction in blue channel clipping, though not completely eliminated.
3. Nikon’s Recommended Workflow:
   • DaVinci YRGB color space with timeline set to DaVinci Wide Gamut.
   • Used CST for input and output transforms: from Nikon log to DaVinci Wide Gamut, then to Rec 709.
   • Observed improved handling of blue channel with minimal artifacts.

Testing ProRes RAW Footage Converted to Cinema DNG

1. Initial Conversion and Analysis:
   • Converted ProRes RAW footage to Cinema DNG.
   • Brought footage into DaVinci Resolve using a custom color management timeline.
   • Compared results with Nikon RAW footage.
2. Transformation Methods:
   • Method 1:
     • Converted with a CST using Blackmagic Design Gen 1 film curve into Rec 709.
     • Observed smoother roll-off in colors compared to Nikon log.
   • Method 2:
     • Debayer processing mode set to Linear, converted to Log C, then to Rec 709.
     • Noted more pleasing and consistent results with smoother color transitions.
3. Further Custom Pipeline:
   • Transformed Cinema DNG footage into Red Wide Gamut in Log3 G10.
   • Exported and re-imported into DaVinci Resolve.
   • Achieved the best rendering of the blue channel, with minimal artifacts and cleaner results.

Results and Analysis

The results were telling. When using automatic color management with HDR timelines, blue channel clipping was evident. However, with our custom pipeline, the issue was significantly reduced, though not entirely eliminated. This pointed to a deeper issue within DaVinci Resolve’s handling of Nikon log footage. The Cinema DNG footage, even when transformed multiple ways, consistently yielded better results than Nikon RAW, indicating a potential flaw in how DaVinci Resolve processes Nikon log data.

We should be clear here: although the issue seems to be with Resolve, the program is only as good as the information it has. Meaning, whoever created the color matrix should go back and take a look. It is unclear if Nikon provided this information via an SDK and Blackmagic Design simply uploaded it, or if Blackmagic Design developed it themselves. Either way, a reassessment of this color matrix is crucial to resolving the blue channel clipping issue effectively.

Practical Advice for Filmmakers

To avoid blue channel clipping in your projects:

• Avoid overexposing blue elements in your footage.
• Use custom color management settings tailored to handle Nikon log properly.
• Implement Nikon’s suggested CST workflow if you prefer a more guided approach.

Conclusion

Our in-depth tests confirm that the blue channel clipping issue stems from DaVinci Resolve’s color management rather than Nikon’s sensor or log format. By adopting the recommended workflows, filmmakers can ensure more accurate color representation and avoid the pitfalls of blue channel clipping.

While technical challenges like these can be frustrating, they also offer an opportunity to deepen your understanding of color management and improve your post-production skills. Remember, every challenge is a stepping stone towards mastering your craft.

If you found this post helpful, don’t forget to give it a thumbs up and subscribe for more insights on video production and post-processing techniques. Follow me on social media for the latest updates and tips, and check out my colleague Derek’s work, who collaborated with me on these tests.

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