Beta Extended, Optical Flow Ready, and 720p Tests

Well, we’ve got a lot of news to report. First off, the Beta has been extended to February 17th. You can download it for Windows at 19lights.com/license/ginger-hdr-beta-download.html.

Also, included in this version is the optical flow workflow. In the Merger application just select Magic Lantern HDR Video, select your video file and the Exposure difference, and click go. That will merge your video to a sequence of EXRs using optical flow. If you use the full speed option you will get a video at, well, full speed. If you use the half speed option, it will use optical flow to merge the underexposed frames but leave the overexposed frames as-is. That tends to result in a much cleaner merge. So if you are delivering for the web at 720p, half speed might be the best option for you.

Of course, it uses optical flow so it’s not the fastest horse in the race. One high priority is to include a lower quality option to get a faster merge in those cases where you don’t have much movement. Also, the CUDA version works but needs to be more robust before releasing it. It’s not fully optimized yet, but so far seems like it should be several times faster.

Here’s a video captured with 720p @ 60fps settings and then “slowed down” to 30fps. The merge looks very clean so far and handles movement pretty well. It has a tough time with anything that moves very rapidly and dramatically changes shape, like the flickering flag in the second shot. Also, I’d recommend staying away from 1600 ISO on the Rebel T2i. In these shots you only need about 3 stops, so if I were to do it over again I’d shoot it at 100/800 ISO.

This video was shot the same way. I wanted to see how well this workflow would do with a fast pan and the results were encouraging. The optical flow solver only goes forward, not backwards. That’s why at the top of the frame you see some major artifacts when the camera is tilting down but looks fine when it’s going up. There are ways to fix it, but of course it will be slower so you probably don’t want that option on all the time.

Ginger HDR, Magic Lantern, and Optical Flow

Every day I get more and more excited about the possibilities of HDR video with Magic Lantern and Canon SLRs. I finally broke down and got a 5D Mark II as well as writing some optical flow algorithms. Obviously, the guys at RE:Vision Effects (Twixtor) and The Foundry (Kronos) have been working on optical flow for years and I’ve spent about 3 weeks, so I’ve got some catching up to do. That being said, there’s no “magic” behind optical flow and all the research is publicly available. The videos above use our custom optical flow solver. They are an encouraging start but there is still a long way to go. There are a lot of “standard” improvements that aren’t in this optical flow solution yet.

So will the results be good enough to actually use? As always, it depends. If nothing moves very fast, the optical flow solver is rock-solid. And so far the tests of pans look clean. But excessive motion causes the typical “warping” artifacts around fast moving objects. Over time it will get better but the problem will never completely go away.
Continue reading

A Little More Beta…

Just a quick note: The beta for Ginger HDR is extended until January 31. The emergence of Magic Lantern has pretty much thrown off the schedule here. We’re working on getting a feasible Magic Lantern workflow ready as well as the Mac version, bug fixes, website work, etc. So we need a little bit of a delay, but hopefully this will be the last one. You don’t need to download a new version, but you will have to re-run the License Manager to fetch a new license.

Magic Lantern Workflow

Happy New Year! For those of you looking at Magic Lantern HDR workflows, I’ve just put up a new video. Support was added for the Merger to merge Magic Lantern HDR videos into a sequence of EXRs a few days ago. Keep in mind: The merger right now is a very, very beta product.