Return-Path: Received: from spike.lmi.net ([66.117.140.17] verified) by media-motion.tv (CommuniGate Pro SMTP 4.2.10) with ESMTP id 4941639 for AE-List@media-motion.tv; Fri, 04 Jan 2013 19:07:38 +0100 Received: from [10.0.1.10] (c-71-198-249-239.hsd1.ca.comcast.net [71.198.249.239]) by spike.lmi.net (Postfix) with ESMTP id BC229154126 for ; Fri, 4 Jan 2013 10:12:30 -0800 (PST) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Apple Message framework v1084) Subject: Re: [AE] Question about flares on transparent layers From: Brendan Bolles In-Reply-To: Date: Fri, 4 Jan 2013 10:12:30 -0800 Content-Transfer-Encoding: quoted-printable Message-Id: <208C9C63-0C3B-40AD-BE53-E7CCC211DF9A@fnordware.com> References: To: "After Effects Mail List" X-Mailer: Apple Mail (2.1084) 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.... >=20 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