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From: Byron Nash <byronnash@gmail.com>
Date: Thu, 2 Feb 2012 15:51:23 -0500
Message-ID: <CANGV+5paVn-D=ay-LQowsR-=MBvUunJgeP_iO++EWU9aNbViTw@mail.gmail.com>
Subject: Re: [AE] Inverse a LUT?
To: After Effects Mail List <AE-List@media-motion.tv>
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It's a 3D LUT from the Arri site, LogC2Video_Rec709.



On Thu, Feb 2, 2012 at 3:13 PM, Brendan Bolles <brendan@fnordware.com>wrote:

> It depends on your LUT.  If it's a 3D LUT, then it can not be inverted in
> general. 1D LUTs can often be inverted.  LUT Buddy has an invert button
> that will be enabled when the LUT is invertible.
>
> In the 3D LUT case, imagine you had a LUT that was used to turn your image
> black and white (desaturate).  As you know, no color operation could hope
> to magically restore the color once it had been taken out.  So that's a
> clue as to why 3D LUTs can't generally be inverted.
>
> If you created your 3D LUT using a series color corrections, your best
> hope is to try to apply them in reverse with inverted settings.  You could
> then make a LUT of that operation to be your inverted LUT.
>
> But usually you just try to come up with something close or deal with it
> on a case-by-case basis.
>
>
> Brendan
>
>
>
> On Feb 2, 2012, at 11:09 AM, Byron Nash wrote:
>
> > I was wondering if there is a way to inverse a LUT? I'm applying an Arri
> Alexa LUT to some footage for VFX work. Some of the elements are graphics
> that need to maintain their color with and without the LUT. We have been
> using a LUT on an adjustment layer and then turning it off before rendering
> it. That way our VFX should be in the correct ranges for Color Correction.
> This works fine for source footage but as soon as you need to put a logo in
> there it gets weird. I'd like to be able to put a reverse of the LUT on the
> logo/graphics and keep all that under the Adjustment layer.  In the past we
> have just sort of used levels and curves to approximate the graphics with
> some success. But I'd like to do it the "right" way.
>
>
> +---End of message---+
> To unsubscribe send any message to <ae-list-off@media-motion.tv>
>

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It&#39;s a 3D LUT from the Arri site, LogC2Video_Rec709.<div><br></div><div=
>=A0<br><br><div class=3D"gmail_quote">On Thu, Feb 2, 2012 at 3:13 PM, Bren=
dan Bolles <span dir=3D"ltr">&lt;<a href=3D"mailto:brendan@fnordware.com">b=
rendan@fnordware.com</a>&gt;</span> wrote:<br>

<blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1p=
x #ccc solid;padding-left:1ex">It depends on your LUT. =A0If it&#39;s a 3D =
LUT, then it can not be inverted in general. 1D LUTs can often be inverted.=
 =A0LUT Buddy has an invert button that will be enabled when the LUT is inv=
ertible.<br>


<br>
In the 3D LUT case, imagine you had a LUT that was used to turn your image =
black and white (desaturate). =A0As you know, no color operation could hope=
 to magically restore the color once it had been taken out. =A0So that&#39;=
s a clue as to why 3D LUTs can&#39;t generally be inverted.<br>


<br>
If you created your 3D LUT using a series color corrections, your best hope=
 is to try to apply them in reverse with inverted settings. =A0You could th=
en make a LUT of that operation to be your inverted LUT.<br>
<br>
But usually you just try to come up with something close or deal with it on=
 a case-by-case basis.<br>
<br>
<br>
Brendan<br>
<div class=3D"im"><br>
<br>
<br>
On Feb 2, 2012, at 11:09 AM, Byron Nash wrote:<br>
<br>
&gt; I was wondering if there is a way to inverse a LUT? I&#39;m applying a=
n Arri Alexa LUT to some footage for VFX work. Some of the elements are gra=
phics that need to maintain their color with and without the LUT. We have b=
een using a LUT on an adjustment layer and then turning it off before rende=
ring it. That way our VFX should be in the correct ranges for Color Correct=
ion. This works fine for source footage but as soon as you need to put a lo=
go in there it gets weird. I&#39;d like to be able to put a reverse of the =
LUT on the logo/graphics and keep all that under the Adjustment layer. =A0I=
n the past we have just sort of used levels and curves to approximate the g=
raphics with some success. But I&#39;d like to do it the &quot;right&quot; =
way.<br>


<br>
<br>
</div>+---End of message---+<br>
To unsubscribe send any message to &lt;<a href=3D"mailto:ae-list-off@media-=
motion.tv">ae-list-off@media-motion.tv</a>&gt;<br>
</blockquote></div><br></div>

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