Thanks for reporting @Zay
The power pin should now accept either a float or RGB value node, for both greyscale and color image nodes, as was the behavior for versions prior to 2026.1.
That fix applies to both grey scale and RGB image node.
But there is also a fix for when loading scenes saved ...

"Fixed Power pin in image texture node to support RGB values again."

Works only for RGB Image but not for Grayscale Image.


Thanks for reporting @Zay
The power pin should now accept either a float or RGB value node, for both greyscale and color image nodes, as was the behavior for versions ...

@nuno1980 RE: Not dispersion, sorry. But yes diffraction in retro-reflectivity?

I see, well, while dispersion has been supported in Octane for a while in some materials, diffraction has not been - until now with the Physical Optics material - which has not got support for retro-reflectivity.
So ...

@non1980 RE: Does Retro-reflectivity have the "dispersion" (in thin- or micro-refraction) option?

If by that you mean to ask how does retro-reflectivity "interact" with dispersion or thin film, then - it doesn't, currently.
Retro-reflectivity only affects specular reflection while both dispersion ...

To add to what Roeland said, I've managed to demonstrate this working in Cinema4D, with a plane with camera-position projection used as UVs with a modulo of 8x4 to get the desired grid repeated: