[Bf-compositor] Clamping (Mix, Math, RGB Curves)

[Bartek Skorupa (priv)]

I must say that I never thought about it this way, but really… just having separate "clamping" node with options of "clamping whites" and "clamping blacks": would solve most of the issues… No matter what my guru:Troy says… :-)

Bartek Skorupa

www.bartekskorupa.com

On 23 maj 2014, at 18:12, Sean Kennedy <mack_dadd2 at hotmail.com> wrote:

> While I understand that internally, all numbers are valid, I agree with Bartek. In everyday film compositing, clamping is necessary. I use it all the time on the math and mix nodes, and even though I know it's not there, I still ALWAYS looks for it on the curves node.
> 
> I would even go so far as to suggest a clamp node. We have the map value node, and in some instances, that does the job, but not all. I love the idea of a clamp node with individual "clamp white" and "clamp black" check boxes. 
> 
>  At R&H, every single compositing setup on every single movie we did had, at the very end of the default compositing template, a clamp node. It made sure that no matter what a compositor did, the blacks wouldn't go too dark and the brights would never get superbright.
> 
> sean
> 
> Date: Fri, 23 May 2014 06:09:54 -0700
> From: troy.sobotka at gmail.com
> To: bf-compositor at blender.org
> Subject: Re: [Bf-compositor] Clamping (Mix, Math, RGB Curves)
> 
> 
> On May 23, 2014 4:46 AM, "Bartek Skorupa (priv)" <bartekskorupa at bartekskorupa.com> wrote:
> > In many cases when using nodes we'd like to clamp output values to visual range (or to range between 0.0 and 1.0).
> There is no “visual range” in Blender's scene referred internal model. All values are valid, and 1.0 has no special meaning.
> The default sRGB output tone response curve only considers 0..1.0, but there is also one that preserves approximately 2 and a bit stops more (values of 4.5 IIRC).
> The transform to a display referred output is a creative decision on what values will become diffuse white. There is no real idea of white in a scene referred model, and again, 1.0 has no significance.
> > Some nodes like Mix or Math nodes have the checkbox for this and it's fantastic.
> Would seem like a bug for scene referred data. Difficult to deal with HDR IBL work.
> > However in many cases we have a need for clamping just "whites" or just "blacks".
> There is no value that is white in a scene referred model. LDR display referred imagery may have a previous diffuse white located at 1.0 when transferred as display linear, but it is merely achromatic in a scene referred model.
> > RGB Curves node in compositor doesn't clamp and when used in Cycles materials it clamps, so we have inconsistency. I'm aware that those are different nodes even though look almost exactly the same.
> Not sure why the Cycles one would clamp, and would seem a bug if it did.
> With respect,
> TJS
> 
> _______________________________________________ Bf-compositor mailing list Bf-compositor at blender.orghttp://lists.blender.org/mailman/listinfo/bf-compositor
> 
> 
> Hey,
> 
> In many cases when using nodes we'd like to clamp output values to visual range (or to range between 0.0 and 1.0).
> Some nodes like Mix or Math nodes have the checkbox for this and it's fantastic.
> However in many cases we have a need for clamping just "whites" or just "blacks".
> Would it be possible to split clamping such that we have two checkboxes: "Clamp Whites" and "Clamp Blacks"? Maybe the names are not the best especially for Math nodes, but I hope you get the idea.
> 
> Another thing is that RGB Curves node has no option for clamping at all. It would be very helpful to have this option.
> When talking about RGB Curves - we have another issue: RGB Curves node in compositor doesn't clamp and when used in Cycles materials it clamps, so we have inconsistency. I'm aware that those are different nodes even though look almost exactly the same.
> I understand that in most cases you wouldn't want to clamp in compositor and would want to clamp when setting materials, but it would be great to have an option (both in compositing and materials). Splitting clamping whites and blacks would be even better.
> 
> What do you think about it?
> 
> Cheers
> Bartek Skorupa
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