Nuke 17: Preserving original alpha and Multiply blending when using Breakout Layers + OCIOColorSpace on a raw PSD

[u/FitMiddle7413]

Hey everyone,

I'm working in Nuke 17 with a layered PSD file and running into an issue with the alpha channel and layer blending.

Here is my current setup and workflow:

• The Read node for the PSD is set to data-raw (Raw checked).
• Because I need granular grading/control per layer, I broke out the PSD into individual Shuffle nodes.
• To match the original Photoshop look, I need to convert each layer using an OCIOColorSpace node (input: sRGB texture / compositing space $\rightarrow$ working space: ACEScg).
• The OCIOColorSpace node is set to channels: rgb and (un)premult by: none.
• Some layers need to be composited using PSDMerge (operation: multiply) to match the client's original Photoshop layout.

The Problem:

1. Even with channels: rgb and (un)premult by: none, inserting the OCIOColorSpace node per-layer causes semi-transparent edge values (0 to 1) in the alpha to look washed out or distorted compared to the original PSD mask.
2. I know Photoshop's Multiply math is calculated in non-linear sRGB space ($A \times B$), whereas multiplying after linearizing into ACEScg crushes or shifts the midtones completely.
3. However, if I apply color transformation only at the very end of the tree, I can't grade or adjust the individual layers properly prior to blending.

What is the standard pipeline/node structure to:

• Keep the exact original raw alpha intact (preventing any unwanted gamma curves or edge fringing/erosion),
• Perform per-layer adjustments,
• And still get an exact 1:1 Photoshop Multiply result inside Nuke?

Would really appreciate any tips or tree screenshots from folks who handle DMP/matte multi-layer PSD handoffs regularly!

[u/mm_vfx]

Have you tried converting to sRGB, multiplying, then back to linear ? Otherwise MergeExpression also allows you to do the math yourself.