ID 366351 - Clamping occurs in a Read or Write node when a non-linear colorspace is applied with color values higher than the alpha in low dynamic range file formats.

Problem summary:
Clamping occurs in a Read or Write node when a non-linear colorspace is applied with color values higher than the alpha in low dynamic range file formats.
 

Customer reported version:
nuke.11.1v2
 

Customer reported platform:
10.11
 

Steps to Reproduce:
1) From Nuke, place a Read node with footage that is a low dynamic range file type (i.e png, tif, sgi) with higher color values than the alpha.

2) Set the colorspace to sRGB, and select the premultiplied checkbox.

3) View the output of the settings, compared to any Raw Data.


Workaround:
Currently, the workflow can be adjusted for the Read node to refrain from clamping by doing the following:

1. Create a Read node in the Node Graph with Raw Data selected.
2. Place an Unpremult node attached to the Read node.
3. Add a Colorspace node with the following settings:
3a. Set the colorspace in as sRGB-D65-sRGB
3b. Set the colorspace out as Linear-D65-sRGB
4. Include a Premult node and view the output.

With the above settings applied, there should be no clamping on the Read node. 


Reproduced by Support in:
Nuke 11.2v3 - Windows 10, CentOS 7, macOS 10.13 High Sierra
Nuke 11.2v1 - Windows 10
Nuke 11.1v6 - Windows 10
Nuke 11.1v1 - Windows 10
Nuke 11.0v4 - Windows 10
Nuke 11.0v1 - Windows 10
Nuke 10.5v7 - Windows 10
Nuke 10.5v1 - Windows 10
Nuke 10.0v6 - Windows 10
Nuke 10.0v1 - Windows 10
Nuke 9.0v9 - Windows 10
Nuke 9.0v1 - Windows 10
Nuke 8.0v7 - Windows 10
Nuke 8.0v1 - Windows 10
Nuke 7.0v10 - Windows 10, CentOS 7, macOS 10.13 High Sierra

Earliest version tested:
Nuke 7.0v10 - This issue appears to be in all versions of the product

Expected Behavior:
The image should appear without clamping when premultiplied on the Read or Write nodes.

Actual Behavior:
There is clamping on the Read and Write nodes where the image will appear with a harsh value when the option for premultiplied is enabled.