Ebb and Flow: Using Magic Lantern at 60fps

11 Dec 13

Recently Swanson Studio was presented with an opportunity to create the video installation for Janet McIntyre’s upcoming show, Ebb and Flow.  The video is an underwater piece that needed to be appropriate for high definition projection with great color depth and integrating slow motion. This presented some challenges, including doing this in the most cost-efficient manner.

Which Camera?

This was our big question. The options included: the Epic, FS700 and 5Dmk3. We decided against the Epic when considering the risk of operating it underwater. A possible repair would mean sending it back to LA and having it out of commission for two weeks or more, which would really mess up our 20/2 shoot schedule.

The second high speed camera that came to mind was the FS700.  It would lock us into a 4:2:0 color space and 1920×1080, which is not great, but we could achieve high speed frame rates. Ultimately we could not find any housing rentals to contain the 4K recording module and the camera, so we eliminated the FS700 as an option.

It looked like our only option would be the 5Dmk3, which shoots in a 4:2:0 color space, has a soft image, and cannot achieve a high speed frame rate. That’s when I started digging into Magic Lantern to see if it could offer any high speed options for the 5Dmk3.  I remembered 14bit RAW had been developed that would provide amazing color depth and a crystal-clear image, but what about high speed frame rate?

60 FPS

Digging around in the forums at Magic Lantern we came across this post by RenatoPhoto.  It detailed how to get 60fps RAW video on the 5Dmk3, which is exactly what we needed.  Although it is not 240fps, it is much nicer than 23.98fps. With any luck using The Foundry’s Kronos we might be able to slow it down even more, possibly getting to 100fps.

Using the ML hack to get 60fps at 1920, it actually squishes the height of the image to 672px.  We were initially afraid that stretching it back out to 1080 would degrade the sharpness of the image, but found the stretched RAW to be much crisper than h264.

Only Four Seconds

So we found our camera!  There was one caveat in that it could only record 4 seconds at 1920×672.  In Renato’s post he recommends 1400×480 in the ML settings to achieve continuous recording, but we decided that four seconds should work for us and allow us the highest quality image we could achieve.  Four seconds at 60fps comes out to about 10 seconds of recorded footage, which meant our shoot would have to be highly coordinated. This meant the models and photographers on the same page, since the camera could only roll for four seconds with a downtime of one second before it could roll again.

The Housing

Another hurdle was the AquaTech housing itself.  We were not able to manually pull focus underwater.  Fortunately, ML preserved the autofocus button on the back of the body. Unfortunately, the underwater housings for the 5Dmk3 are not the most accurate and the buttons on the back of the housing do not always align with the buttons on the back of the camera. Brandon (AC) and I came up with the solution of paper tap to hit the buttons. For the most part this was effective, but occasionally Marcus (DP) would be forced to surface due to the body shifting inside of the housing and the focus button no longer working.

The Results

After lots of patience and adapting to situations on the fly, we came away with a lot of amazing footage.  Below is an example of one of the clips we shot, showing the process of slowing the footage down, grading, and finally running it through Kronos.

Next week I will post a our actual work flow.

If you would like more information on Janet’s show, Ebb and Flow, please see our previous post here. You can also buy tickets here.