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References: <list-4941640@media-motion.tv>
Date: Wed, 9 Jan 2013 00:55:28 -0800
Message-ID: <CANL=31HVE3+C6ydk_3dZHCk+AyesPeBp0AV5_=2O0PCqg1-0xg@mail.gmail.com>
Subject: Re: [AE] Question about flares on transparent layers
From: Darby Edelen <dedelen@gmail.com>
To: After Effects Mail List <AE-List@media-motion.tv>
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While light is additive I don't think that can be used as a blanket
statement to justify using an additive blend mode anytime light is involved
:)  In fact I'm pretty sure that real lens flares aren't additive but a
weighted blend very much like the 'normal' blend mode in AE.

UnMult would be the 'correct' way to go but I'll be the first to admit that
I'll use 'Add' when I think it looks better!

UnMult is available free (with registration) from Red Giant:

http://www.redgiantsoftware.com/products/all/knoll-unmult-free/

Also as an alternative to UnMult you can apply Shift Channels, set "Take
Alpha From" to Luminance and either change the layer's blend mode to
Luminescent Premultiply (works in all bpc settings) or apply Remove Color
Matting and disable Clip HDR Results (only works in 32bpc).  Screen is also
a decent approximation in 8 or 16bpc.


On Fri, Jan 4, 2013 at 10:12 AM, Brendan Bolles <brendan@fnordware.com>wrote:

> On Jan 4, 2013, at 8:17 AM, Steve Oakley wrote:
>
> > FWIW I have no idea with lens flare filters don't generate their own
> alpha....
> >
>
>
> Because in nature light is purely additive thing and never covers up the
> background so much as obscures it by blowing out to white.  So keeping the
> opaque AE layer on top of the comp and using Add or Screen is the proper
> way to simulate that.
>
> In a compositor that uses premultiplied pixels internally, you could
> create a layer that had a flare and no alpha, which mathematically results
> in the same thing as AE's straight-pixel opaque layers set to Add.
>
> The UnMult effect is best for situations where you're rendering out an
> element for a program doesn't have Add or Screen transfer modes (are there
> any more like that?).  Since the Normal transfer mode involves a multiply
> by alpha, UnMult creates an alpha and divides by it to try to get the
> result to come out the same.
>
>
> Brendan
>
>
> +---End of message---+
> To unsubscribe send any message to <ae-list-off@media-motion.tv>
>

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<div dir=3D"ltr"><div>While light is additive I don&#39;t think that can be=
 used as a blanket statement to justify using an additive blend mode anytim=
e light is involved :)=A0 In fact I&#39;m pretty sure that real lens flares=
 aren&#39;t additive but a weighted blend very much like the &#39;normal&#3=
9; blend mode in AE.<br>
<br></div><div>UnMult would be the &#39;correct&#39; way to go but I&#39;ll=
 be the first to admit that I&#39;ll use &#39;Add&#39; when I think it look=
s better!<br><br>UnMult is available free (with registration) from Red Gian=
t:<br>
<br><a href=3D"http://www.redgiantsoftware.com/products/all/knoll-unmult-fr=
ee/">http://www.redgiantsoftware.com/products/all/knoll-unmult-free/</a><br=
><br></div><div>Also as an alternative to UnMult you can apply Shift Channe=
ls, set &quot;Take Alpha From&quot; to  Luminance and either change the lay=
er&#39;s blend mode to Luminescent Premultiply (works in all bpc settings) =
or apply Remove Color Matting and disable Clip HDR Results (only works in 3=
2bpc).=A0 Screen is also a decent approximation in 8 or 16bpc.<br>
</div></div><div class=3D"gmail_extra"><br><br><div class=3D"gmail_quote">O=
n Fri, Jan 4, 2013 at 10:12 AM, Brendan Bolles <span dir=3D"ltr">&lt;<a hre=
f=3D"mailto:brendan@fnordware.com" target=3D"_blank">brendan@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"><div class=3D"im">On Jan 4, 2013, at 8:17 AM=
, Steve Oakley wrote:<br>
<br>
&gt; FWIW I have no idea with lens flare filters don&#39;t generate their o=
wn alpha....<br>
&gt;<br>
<br>
<br>
</div>Because in nature light is purely additive thing and never covers up =
the background so much as obscures it by blowing out to white. =A0So keepin=
g the opaque AE layer on top of the comp and using Add or Screen is the pro=
per way to simulate that.<br>

<br>
In a compositor that uses premultiplied pixels internally, you could create=
 a layer that had a flare and no alpha, which mathematically results in the=
 same thing as AE&#39;s straight-pixel opaque layers set to Add.<br>
<br>
The UnMult effect is best for situations where you&#39;re rendering out an =
element for a program doesn&#39;t have Add or Screen transfer modes (are th=
ere any more like that?). =A0Since the Normal transfer mode involves a mult=
iply by alpha, UnMult creates an alpha and divides by it to try to get the =
result to come out the same.<br>

<br>
<br>
Brendan<br>
<br>
<br>
+---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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