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 4579451 for AE-List@media-motion.tv; Tue, 03 Jan 2012 20:13:49 +0100 Received: from [192.168.1.132] (c-71-198-249-239.hsd1.ca.comcast.net [71.198.249.239]) by spike.lmi.net (Postfix) with ESMTP id 2C0961540FA for ; Tue, 3 Jan 2012 11:20:27 -0800 (PST) Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (Apple Message framework v1084) Subject: Re: [AE] HDR-esque technique for high-speed footage From: Brendan Bolles In-Reply-To: Date: Tue, 3 Jan 2012 11:20:26 -0800 Content-Transfer-Encoding: quoted-printable Message-Id: References: To: "After Effects Mail List" X-Mailer: Apple Mail (2.1084) On Dec 31, 2011, at 11:13 AM, Dave Bittner wrote: > I've got some footage from a Photron high speed camera that's = presented an interesting challenge to me. The camera records a sequence = of images that have a 48 bit depth, which is a large dynamic range. On = export to QuickTime, however, you are forced choose a bracketed range of = 8 bits. After multiple exports, I'm left with a movie that's = underexposed, one that's properly exposed, and one that's overexposed. I = want to combine then, HDR-style, to show the details in the highlights. = (The footage is a series of explosions, so there's a lot going in the = highlights.) This is interesting. So when you say bracketed range, do you mean that = you're only able to choose 1/6 of the histogram, or that you set your = white point and it crams everything from black to that point into an = 8-bit file? The latter is essentially what you get from doing different = exposures in a camera, the former would be unusual. Anyway, it is possible to do an HDR merge in After Effects. If I = weren't so lazy, I would have put up a video tutorial by now. I'll try = to describe how to do it photo-style here. If you have the 1/6 = histogram situation, it would be a little different. 1. Set your project to a 32-bit linear space. 2. Import your bracketed photos, drag them into a comp. AE will have = converted them from sRGB to linear. Many HDR programs calculate the = actual response curve for the camera, obviously AE is just using the = sRGB curve. (Do the Photron people tell you if they're applying a = gamma?) 3. Pick one photo to be your base, and leave it be. Then take the next = darker image (captured at -1 stop) and use the Exposure filter to = brighten back up by +1 stop. Hide the other photos for now. If your camera truly had a perfect sRGB response and the photos were in = perfect alignment, the brighter pixels from the base image would now = match the mid-range pixels from the -1 stop image. You can tweak the = exposure controls and re-align the image to try to get them to match as = closely as possible. The darker pixels from the -1 stop image will have = a lot of noise in them, and the brighter pixels will add detail into the = 1.0-2.0 range. 4. Comp the useful parts of the brightened -1 stop image onto the base = image. Do this in AE by dragging the -1 stop image into AE again to be = used as a luma matte for the exposure-adjusted version. Apply shift = channels to set RGB to Luma. Set this layer as the other layer's luma = matte. Then apply Levels and set input white to 0.5 and input black to = something like 0.25. This will keep all the 1.0-2.0 overbrights and = blend between the two pictures in the 0.5-1.0 range. We're just using = Normal transfer mode here. 5. Repeat for all the other photos, increasing your -2 stop exposure by = +2 stops, -3 to +3, etc. The Levels settings will be the same because = you apply those to the un-adjusted images. Sorry if that's hard to follow. I realize a video tutorial would be = better. Brendan