Canon 5D face-off: MkIII vs MkII

If you’ve been living with the Canon 5D Mk II for the last three years and have a workflow in place, you may be wondering if it’s worth moving up to the MkIII. I believe the answer is a resounding yes – especially if you’re doing your own post…

The compression: I-frame vs GOP

One of the main decisions you’ll face on upgrading is whether to move from shooting with GOP compression to I-frame. GOP compression basically uses three types of frame: intra-frame, bidirectional and predictive frame. Without getting too deep into how these are structured and what they all do, the I-frame is the only standalone frame containing all information; the B and P frames only display the information that changes from that I-frame, with the P frame only displaying changes from frames to itself and the B frame referencing changes in the frames before and after itself.

The I-frames refresh the information because with GOP compression the further you go before an I-frame, the more errors start to build, but the closer the I-frames are together the larger the bitrate will be. In the 5D MkII, for example, there were 12 B and P frames between each I-frame. In the 5D MkIII, when shooting GOP there are only 10 B and P frames between each I-frame, resulting in improved image quality. (This is one of many changes to the codec.)

The 5D MkIII also does Intra-frame encoding. This means it encodes each frame as a standalone picture, so no frame is dependent on any other frame to reproduce the original image. This is currently much better to edit with, because your computer isn’t constantly looking at all the different frames in order to display an image. Plus, when you make a cut with a GOP movie, your computer has to look around and create a whole new I-frame where you made the cut, and when grading you are going to get artefacts and anomalies because you are colouring footage that only exists virtually. I-frame-only codecs bypass this, making editing smoother, faster with less strenuous for your CPU.

The Workflow: Shooting

When you shoot with your new 5D MkIII after editing with it once, you won’t want to use the GOP version again – stay I-frame only. Navigating through the new 5D MkIII menu structure is very easy, and simple to set.

The workflow: Ingest

To ingest, I used Sonnet’s dual-bay CF card to Express34, and if you have an Express34 port then this is one of the fastest ways to ingest. If you have Thunderbolt then you can couple it with Sonnet’s upcoming Express34 to Thunderbolt reader, so you’ll be able to pull the data off at the speed of the card. For lots of footage, I would recommend this.

The workflow: Editing

Editing in FCP7

One thing that surprised me was the 5D MkIII’s immediate and seamless integration with FCP7. As an added bonus, render times for the 5D MkIII I-frame footage are less than half the length of render times for 5D MkII raw H.264 (admittedly this is slightly irrelevant because who edits raw H.264 DSLR footage more than once?). When working with ProRes LT and HQ with the same effect applied, render times where pretty much the same as the I-frame footage. Trimming was quicker and much more responsive, so you got realtime jogging and cuts happened instantaneously.

In the past, the most common workflow for all of us shooting DSLR was to ingest the footage and transcode it to ProRes LT (around 35Mb/s), sometimes ProRes HQ (120Mb/s). But given that the bitrate of raw footage rarely exceeded 40Mb/s, stepping down to ProRes LT didn’t lose you much, if any, quality, and the speed at which you could edit shot up. Your new I-frame 5D MkIII footage is now over 60Mb/s, and because of the lack of IBP frames edits like a dream. You won’t want to transcode to anything – especially not ProRes LT – because you will definitely be almost halving the quality. If you are shooting I-frame and need ProRes for any reason, then your new 5D MkIII needs ProRes HQ. (If you are shooting GOP then stick with ProRes LT.) But my advice is: avoid transcoding, where possible edit natively.

Editing in FCPX

Like me, I imagine a lot of DSLR users who migrated to FCPX got excited about the idea of cutting DSLR footage natively, tried it, and decided to go back to ProRes. It’s quicker, more responsive and more reliable, and that matters when you are using FCPX’s cursor-scrolling previews to find your way around your clips.¬†5D MkIII I-frame footage again gives you faster performance. You may not notice this with a couple of clips, but try playing back a long edit you are working on and you will start to see a difference.

Editing in Premiere Pro

This is by far the fastest workflow for cutting your 5D MkIII footage. It’s common knowledge now that Premiere Pro, optimised correctly, can run rings around other NLEs, especially when editing DSLR footage.

Let’s take a look at a pretty common situation: editing for fast delivery to the web. Here, using the Adobe Media Browser you could get your shot (which you monitored and adjusted the audio on in-camera) straight into Premiere and edit off the CF card. A quick top and tail of the shot, a couple of cutaways, add your branding and export to Flash through Adobe Media Encoder – done. With a 5D and Adobe, you can have your breaking news professionally produced and on the web within minutes of it happening. Without the 5D MkIII’s I-frame footage, rendering alone would slow you down, making a transcode to something else necessary, and encoding would take twice as long.

Be wary of editing multiple streams from the CF card, though – remember you only have a read/write speed of 90Mb/s or so from that card which is only fast enough for one stream. This is not a stable workflow, but it is a fast one.

Because it is AVC, playback will happen through either the Adobe Mercury Playback software or engine, depending on the availability of compatible GPUs. In terms of rendering time, Premiere again is impressive, rendering The 5D Mk II footage at the same speed as the I-frame Mk III (if you have a CUDA card ignore this bit as you won’t have to render most things you do). Without a CUDA card, though, problems with H.264 GOP will start to show as sustained playback stresses your CPU, generally making your workflow unstable.¬†Shooting I-frame will be less processor intensive, more stable and faster over a prolonged period of time.

Editing in Media Composer 6

Most people will now be familiar with editing and ingesting to Avid via the AMA function. In short, this turns Avid into a native NLE rather than a DNxHD-only NLE. This means no transcoding and again, with your I-frame-only footage you get the benefit of editing something like DNxHD without the hefty bitrate, transcode times or increased chance of bottlenecking from slower connection HDDs (USB2, Firewire 800, etc.).

If you need DNxHD, your only real choice for 5D footage is DNxHD 120 (120Mb/s), and this has been the codec of choice for Media Composer DSLR editors in the past. These days, use AMA files – they’ll cut just as well and transcoding takes ages. With I-frame 5D MkIII footage, you won’t see much benefit from transcoding to DNxHD but, like using ProRes HQ, you will be doubling the demand on your bandwidth from your HDD, limiting the amount of streams you can cut and increasing the chances of bottlenecking.

Grading and colouring: DaVinci Resolve

It is going to be even easier to make your footage look incredible in Resolve now that you have this I-frame codec. The problem I found when grading DSLR footage in the past was its tendency to get noisy and blocky fast, with artefacts and anomalies appearing all over the place. This was a result of the heavily compressed GOP codec, as well as it being 4:2:0 colour subsampling (the anomalies this caused didn’t go away even if you transcoded to ProRes HQ). The I-frame 5D MkIII footage is still 4:2:0 subsampling, so you will still have to treat it right to deal with a restricted colour space, but you aren’t going to be fighting against the problems encountered with grading GOP-based footage and it won’t turn as blocky and noisy on you as quickly.

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