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ASC CDL Node: Clamps
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Description

According to the ASC CDL specification, there should be no clamps on the slope, offset, or power of the ASC CDL transform.

In Blender, there is.

Event Timeline

Troy Sobotka (sobotka) set Type to Bug.
Troy Sobotka (sobotka) created this task.
Troy Sobotka (sobotka) raised the priority of this task from to Needs Triage by Developer.
Sergey Sharybin (sergey) triaged this task as Needs Information from User priority.

Blender doesn't have "ASC CDL" node. Rest of the report please translate to English (at least so Blender community can understand what's it's all about!). Following report bug guidelines will also be a god idea to do.

ASC CDL is in the Offset/Power/Slope (ASC-CDL) in the color balance node, The default correction formula there is Lift/Gamma/Gain so it's a bit hidden.

Sorry.
System Information
Operating system and graphics card
Linux amd64 Debian Squeeze

Blender Version
Broken: 3b1acd
Worked: Don't think it ever did

Short description of error
Line 31 of COM_ColorBalanceASCCDLOperation.c uses a CLAMP operation. This breaks all scene referred imagery out of Cycles, as well as goes against the specification which should never be clamped against display referred values. See https://en.wikipedia.org/wiki/ASC_CDL for more information.

Exact steps for others to reproduce the error
Load a Color Balance Node, flip to ASC CDL. Impossible to get correct results as the values are clamped.

I concur with T & B...

Well, sure enough the wiki does not take into account any issues caused by machine arithmetic and only shows math side ;)

So think we should still prevent negative values from happening before calling a pow(). Clamping from the top is not needed here indeed.