Noise Reduction Microscope for Fusion
How to Create an A/B Difference Viewer for Noise Reduction in DaVinci Resolve Fusion
When performing noise reduction for visual effects, it is crucial to know when you have pushed the settings too far and started losing detail. Users of the Color page in DaVinci Resolve are likely familiar with the "Highlight" A/B mode, which displays a difference matte showing exactly what changes are being made to the image.
However, this feature is not native to the Fusion page viewer. This guide will walk you through how to manually build this tool to effectively evaluate noise reduction in your compositing workflow.
Step 1: Setting Up the Workflow (Log vs. Linear)
Before building the viewer, it is important to establish where noise reduction fits in the pipeline.
Linear Conversion: When compositing log footage (such as Sony S-Log3), the goal is usually to get into linear space as quickly as possible. You can use the Cineon Log tool to convert your footage to linear.
Important Clipping Setting: When using the Cineon Log tool, the default clipping is set to "None." This can create negative values outside the bounding box, which causes issues if you crop later. It is highly recommended to change the clipping mode to Domain to ensure edges cancel out to zero.
Applying Noise Reduction: Following traditional VFX methods, apply your noise reduction in Log space (before the linear conversion). Add a Noise Reduction node immediately after your footage.
Pro Tip: Never use the "Faster" setting on the noise reduction tool. Always set it to Better; otherwise, the results are comparable to a simple blur.
Step 2: Building the A/B Difference Viewer
To recreate the A/B difference view found on the Color page, you only need two specific nodes in Fusion.
The Channel Booleans Node
Add a Channel Booleans node.
Operation: Change the operation to Divide. This mathematically matches the Color page functionality the closest.
The Connection: Connect your original plate and divide it by the noise-reduced version. Since you are dividing the image by itself (initially), the result will be a code value of 1 (white).
The Brightness Contrast Node
To make the difference visible, add a Brightness Contrast (BC) node after the Channel Booleans.
Adjustment: Set the brightness to -0.5.
Result: This shifts the white image down to middle gray (code value 0.0), allowing you to clearly see positive and negative pixel changes.
Step 3: Evaluating Your Noise Reduction
With the Brightness Contrast node viewed, you can now adjust your noise reduction settings. As you increase the threshold, the gray viewer will reveal the "difference"—showing you exactly the noise and detail being removed.
Tips for Evaluation:
Desaturate: Taking the saturation out of the viewer can sometimes make it less distracting when evaluating how far to push noise reduction.
Check Individual Channels: Use keyboard shortcuts R, G, and B to view individual color channels.
Red: Often the noisiest channel, particularly for skin tones or green screens.
Green: usually the cleanest channel containing the most data.
Blue: Typically somewhat noisy.
Watch for Artifacts: If using temporal noise reduction, be careful with moving elements like hair, which can artifact quickly. It is suggested to start with a setting of "1" (evaluating one frame before and after).
Step 4: Saving as a Macro for Future Use
You don't need to rebuild this every time. You can save these nodes as a preset or macro.
Select the Channel Booleans and Brightness Contrast nodes.
Right-click on a node and select Settings > Save As.
Name the file (e.g., "Noise Check").
Now, whenever you are in Fusion, you can press Shift + Space, search for "Noise Check," and your pre-configured difference viewer will be ready to use immediately.
