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

[Bartek Skorupa (priv)]

It is possible to clamp (blacks and whites individually even), but whenever I want to do it I have to add gazillion nodes. It takes time. My intention is to make it with a single click.
How much time did it take you to set up this fantastic node tree of yours? If it's more than one second - itś too much. It should be: Decision => 1 second later: DONE.


Bartek Skorupa

www.bartekskorupa.com

On 24 maj 2014, at 00:10, Sean Kennedy <mack_dadd2 at hotmail.com> wrote:

> Ah, great idea! We could even set one up with RGB, one on each channel, and save it as a nodegroup.
> Thanks! So obvious, don't know why we didn't think of this. :)
> 
> I'm going to set one up today.
> 
> sean
> 
> > From: dnicolas at gmail.com
> > Date: Fri, 23 May 2014 19:07:28 -0300
> > To: bf-compositor at blender.org
> > Subject: Re: [Bf-compositor] Clamping (Mix, Math, RGB Curves)
> > 
> > Hi all, I don't know how Blender's handles colors internally but
> > wouldn't this work?
> > http://www.pasteall.org/pic/show.php?id=71736
> > (or are the V values already mapped to 0-1 from the separate node?)
> > 
> > Cheers,
> > 
> > 2014-05-23 18:46 GMT-03:00 Sean Kennedy <mack_dadd2 at hotmail.com>:
> > > Could we set the value of the clamp? It could come in as defaults of 1.0 and
> > > 0.0, but we could alter it to whatever we wanted. At R&H, most of the time
> > > we clamped brights around 14-16. We'd only turn it down under that if we got
> > > bad pixels when rendering.
> > >
> > > If you had a superbright red, like R 12, G 3, B 4, and you put a clamp of 1
> > > on it, obviously it's going to set each value to 1, so what was red now
> > > reads as white. But it would still be useful.
> > >
> > > After Effects clamp tool
> > >http://cdn.aescripts.com/media/catalog/product/cache/1/image/800x600/040ec09b1e35df139433887a97daa66f/f/t/ft-clamp-ui_1.png
> > >
> > > Nuke clamp is in the color grade node
> > >http://docs.thefoundry.co.uk/nuke/63/pythondevguide/_images/getMinMax_01.png
> > >
> > > I'm not posting the images to say "this is how we should do it", but rather,
> > > to say it is useful and professional compositors would indeed use it often.
> > >
> > > In fact, I was working on a shot this week that could have used it. I was
> > > given stock footage from a client, and I have no idea how much they'll color
> > > correct it in post once I deliver the final vfx shot. SO I have to make sure
> > > all my blacks are in line with what is in the plate. I put a gamma on the
> > > plate just to view the black levels and see how they match up when pushed
> > > really far.
> > >https://dl.dropboxusercontent.com/u/10553822/clamp_blacks_01.jpg
> > >
> > > Since we don't have a clamp, I ended up putting a mix node right after the
> > > stock footage node, setting it to Lighten, and making the color over it
> > > black. then I slowly raised it while watching until the blacks all came in
> > > line. Would have been much easier to sample the value of the darkest dark I
> > > wanted in the shot, throw a clamp node on with the black clamp set to those
> > > values.
> > >
> > > In fact, at R&H, the Black Clamp node let you set an individual value for R,
> > > G, and B. And it had a color picker so you could just sample the image and
> > > the values would fill in automatically.
> > >
> > > Anyway, just throwing out my $0.02. Obviously I've found a workaround and
> > > can live with it, but it would sure be great to someday see a clamp node.
> > >
> > > ________________________________
> > > Date: Fri, 23 May 2014 14:21:40 -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 1:56 PM, "Bartek Skorupa (priv)"
> > > <bartekskorupa at bartekskorupa.com> wrote:
> > >
> > >> When I say: "clamp blacks" I always mean: set every value below 0.0 to
> > >> 0.0.
> > >> When I say: "clamp whites" I always mean: set every value above 1.0 to
> > >> 1.0.
> > >> Every compositing artist will know what I mean.
> > >
> > > If we can generate a clamp / scale node, I am all for it.
> > >
> > > I am saying there is no concept of white in a scene referred model, and as
> > > such, you have to be careful as to not write nodes that break the system.
> > >
> > > It is that simple. No white. No brighter than white. So sorry, “Every
> > > artist...” is actually “Every artist unfamiliar with HDR work.”
> > >
> > > So a clamp node _must_ not make the erroneous assumption that 1.0 means
> > > anything special, and rather provide for an arbitrary value range.
> > >
> > > If this all seems like speaking an alien language, it is precisely why I
> > > chimed in and said “Whoa.”
> > >
> > > There are already nodes that are broken because of erroneous assumptions. It
> > > would be a shame to make more.
> > >
> > > With respect,
> > > TJS
> > >
> > >
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