[Bf-cycles] Color (un)premultiply

[Adriano Oliveira]

See exemple atached:

Render with transparency and saved as TIF 16bits RGBA.
Composed in Photoshop over a red BG.

Adriano A. Oliveira


2012/12/12 Brecht Van Lommel <brechtvanlommel at pandora.be>

> Hi,
>
> As far as I know, the new color management changes in 2.64 should not
> introduce any extra fringes compared to before. If that's the case it
> would be interesting to understand why.
>
> This option is definitely a color management option though, and
> affects compositing as well, I don't think it's correct to place it in
> the Film panel. The exposure option in the film panel will be removed
> eventually, it's a separation option but it should really be using the
> color management settings instead. Maybe it should be there anyway,
> but ideally we could find a better way to communicate things rather
> than duplicating the option, or maybe the default value should be
> changed.
>
> In any case, the unpremultiply option is something that should be
> avoided when possible, there is no right way to use it, depends a bit
> on the image what looks best, but the result will be subtly wrong
> either way. Ideally you should never do color space conversion on an
> image that has an alpha channel, which means working in linear float
> color space and only doing the color space conversion at the very end
> when everything is composited together. Though it's not always
> possible to set up an entirely correct color pipeline with external
> tools involved.
>
> Brecht.
>
> On Wed, Dec 12, 2012 at 3:34 PM, Adriano Oliveira
> <adriano.ufrb at gmail.com> wrote:
> > Since 2.64 I've problems with transparency finges when editing render
> > outside Blender.
> > Last week I discover the "Color unpremultiply" option and every thing is
> > fine again.
> >
> > I supose that many others like me are having hard times dealing with
> > premultiplied fringes due to new Color Management been so far from render
> > options.
> >
> > My proposal is to merge Color Management in the FILM slider at Render
> > Options.
> > At least, "Color unpremultiply" option should be near TRANSPARENCY
> option,
> > even if it is repeated in Color Management, like Exposure seams to be.
> >
> > Adriano A. Oliveira
> >
> > _______________________________________________
> > Bf-cycles mailing list
> > Bf-cycles at blender.org
> > http://lists.blender.org/mailman/listinfo/bf-cycles
> >
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