[Bf-committers] Color correction in sequencer.

Xavier Thomas xavier.thomas.1980 at gmail.com
Thu Dec 11 00:28:02 CET 2008


they are not really intuitives, but they works like "Levels" in gimp
Lift must set the black level
Gain the white
and Gamme the mid point

The problem here is that the the values are manipulated for :
- "1,1,1" to be "no change value"
- Values between 0 and 1 to darken the image
- An "inverse" button tho permit values > 1 wich brighten the image
More than being unintuitives, it does not permit full control (inversing
gain invers for all channels)

What solution:
- Curves will take big UI
- Levels maybe also

But it is not preferable to do this as an sequencer effect, This will permit
the user to choose the effect acording to the type of correction he wants to
make (Level, curves, ...)

For primary color correction this is not really important as for me "Levels"
and "Lift/Gamma/Gain" are the same with different way of setting the
parameter and they can be done with curves.

But if complex secondary collor correction (like changing saturation  and
value acording to hue with a curve, ...) is going to make is way in blender
the user must choose the one he wants

Note that with nodes doing a "not so complex secondary color correction"
(like the exemple below) requires:
-color space conversion
-doing a difference map with a constant value
-using this map as factor for color

It will need about 10 nodes and that is uaualy done in one in shake or with
one effect in finalcut.

I am interested in this kind of stuff and I can code it but as I said if is
going to be used by nodes, sequencer and image editor ther must be a way to
unify it.

xavier

2008/12/10 Campbell Barton <ideasman42 at gmail.com>

> On Thu, Dec 11, 2008 at 9:33 AM, Xavier Thomas
> <xavier.thomas.1980 at gmail.com> wrote:
> > Yes, that is what I ment but is it ok to add an UI parameter "ofset" with
> is
> > button "Inv ofset" at the side of the Lift gamma and gain parameters
> because
> > the UI will get really charged.
> >
> > And what about an image treatment library, because I already have made
> this
> > function in my keyer node and crating a color correction node with these
> > controls might be usefull also: this will result in a lot of code
> > duplication.
> >
> >
> > 2008/12/10 Dalai Felinto <dfelinto at gmail.com>
> >>
> >> Hi Xavier.
> >>
> >> Can't you do a do_version()?
> >> In readfile.c you can see a lot of parameters that need to be updated
> >> over Blender version.
> >> If what you need is a simple offset for old blender files work in the
> >> same way as new blender files (with this bug fixed), this should work.
> >>
> >> I didn't see the bug or this part of the code, but do_version()
> >> sometimes is the better way to go.
> >>
> >> Cheers,
> >> Dalai
> >> http://blenderecia.orgfree.com
> >>
> >> 2008/12/10 Xavier Thomas <xavier.thomas.1980 at gmail.com>:
> >> > Hello,
> >> >
> >> > Lately, I was trying to implicate me in blender developement,  and
> >> > begining
> >> > with small things (after the keyr node) I  desided to correct this
> bug:
> >> >
> >> >
> http://projects.blender.org/tracker/index.php?func=detail&aid=18010&group_id=9&atid=125
> >> >
> >> > Basicly the lift parameter of color correction in sequencer works more
> >> > like
> >> > a "value" color correction than a "lift" (exept that it work on RGB
> >> > channel
> >> > separately so I think "ofset" is more apropriate then "value")
> >> >
> >> > Fixing it would be simple but old files that use this parameter will
> >> > have a
> >> > diferent render result, and after discussing with Matt Ebb on IRC it
> >> > seems
> >> > that this is not acceptable.
> >> > So the only solution to have a proper color correction in the
> sequencer
> >> > is
> >> > to add an "ofset" parameter. Is this OK ? (maybe the UI will get too
> >> > compact)
> >> >
> >> > Further, why do not put this kind of function in an image library so
> it
> >> > will
> >> > be accesible form other part of the program (nodes and maybe image
> >> > editor)
> >> > like the quick blur function in the nodes CMP_util.h
> >> >
> >> > Sorry to disturb, I know lot of you are really buzzy but I prefer to
> get
> >> > good directions before coding.
> >> >
> >> > Thanks
> >> >
> >> > Xavier
> >> >
> >> > _______________________________________________
> >> > Bf-committers mailing list
> >> > Bf-committers at blender.org
> >> > http://lists.blender.org/mailman/listinfo/bf-committers
> >> >
> >> >
> >> _______________________________________________
> >> Bf-committers mailing list
> >> Bf-committers at blender.org
> >> http://lists.blender.org/mailman/listinfo/bf-committers
> >
> >
> > _______________________________________________
> > Bf-committers mailing list
> > Bf-committers at blender.org
> > http://lists.blender.org/mailman/listinfo/bf-committers
>
> Recently I tried making sense of the sequencer's color functions and
> found them quite confusing. Even after tweaking them for 5min I don't
> really understand what they do exactly.
>
> Id much prefer convert these values into either, gimp/photoshop color
> 'Levels' or 'Curves'.
> Curves are already used in other parts of blender so I'ts probably not
> that hard to make this change,
>
> Peter, if your reading, Could these settings be converted to curves?
> (even a close approximation would be ok I think)
>
> --
> - Campbell
> _______________________________________________
> Bf-committers mailing list
> Bf-committers at blender.org
> http://lists.blender.org/mailman/listinfo/bf-committers
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.blender.org/pipermail/bf-committers/attachments/20081211/b99bc360/attachment-0001.htm 


More information about the Bf-committers mailing list