So, after rotoscoping hundred of shapes in Silhouette, all with motion blur, you export the shapes to Nuke splines. Once imported into Nuke, you are wondering why the Alpha channel looks different than it did in Silhouette. This is because the default Nuke Viewer settings apply a LUT to not only the RGB channels, but the Alpha channel as well.
To ensure that the Alpha channel displays the same in Nuke as it did in Silhouette, there is a specific Nuke > Viewer control that needs to be enabled.
- Select the Nuke > Viewer node, right-click in the Viewer and choose Viewer settings to open them.
- Enable “apply LUT to color channels only”
(Note: You can make this a default Viewer setting in the Nuke preferences.)
The Alpha channel in Nuke will now match Silhouette.
Here’s an example of the difference you will see when the Viewer LUT is applied to all four channels instead of just RGB. Note how the Nuke example expands the soft areas of the matte.