If you are a Canon 5Dmk2 fanboy you may want to shut your eyes. The lowly Panasonic GH1 just got supercharged with a firmware hack that makes a great HDSLR video camera even better. Here is my list of things that make the GH1 a better video camera than the 5D. First let’s take a look at the 800-pound gorilla in the room, The Canon has a full frame 35mm sensor, therefore, there is no crop factor when using 35mm lenses. Canon’s full size sensor is 4 times the size of the 4/3rds sensor in the GH1, which also means that the Canon must compress 4 time the data for the same bandwidth, all thing being equal (which they are not.) Supposedly the 5D is writing data at 35Mbs, compared to the (stock) 17Mbs of the GH1, which means that it’s still throwing away half again as much data as the GH1 (4 time the sensor and only twice as much data as the GH1).

My GH1 Camera Rig

But there’s more, the GH1 hack also enables the 1080P mode using MJPEG compression at 100Mbs for short shots. While this setting is kind of like using nitrous and it’s really pushing the limits of the camera, it is a real boon if you want to get the highest quality video possible. The advantage that motion JPEG has over h.264 is that it only uses spatial compression instead of the temporal and spatial compression of h.264. This means prettier pictures. His holiness, Phillip Bloom posted a great blog post on what the firmware hack brings to the GH1 which you can read on his blog.
I’ll admit that image quality is close enough between these two cameras that the 5D might win if that were the only issue. But the GH1 is a far more usable camera than the 5D, First off, for shooting video you can’t beat the fold out LCD screen on the GH1. It’s just better than the Live View screen on the 5D, period, even with a Z-finder. Second, the GH1 has continuous auto focus when using the kit lens. With 5D in live mode, you are stuck with whatever focus you had when you started recording. Thirdly, even un-hacked the GH1 can shoot 30fps 1/2 speed slow motion. You just shoot at 60fps 720p and play back the footage at 30fps, no frame blending or doubling, just plain good old fashioned over-cranking.
Okay, Let’s talk about glass. The 5D still uses an optical viewfinder, which means it has a pentaprism and a mirror, which it must flip up to take video, which, of course, makes the optical viewfinder unusable. This arrangement also means that the Canon has a deep flange distance. the flange is the measurement from the back of the lens to the surface of the sensor. Traditional film and video lenses have a short flange distance and don’t work well with 35mm SLR bodies. The GH1 has no optical viewfinder and therefore has a very short flange distance, which means it can use practically any 35mm SLR, video or film lens that someone is willing to make a adapter for. There is even a PL mount adapter that cost as much as the GH1, so that you can use cine lenses that cost 100 times as much the GH1. I use all my old Canon FD SLR lens as well as some Minolta, Olympus, and16mm film lenses and even cheap CCTV lens with my GH1.
Finally, let’s take a look at the form factor. The 5D is big and relatively heavy DSLR. Great if you’re trying to impress other photographers or the bridesmaids at a wedding shoot, not so good if you’re actually trying to shoot steady handheld video. The GH1 is lighter, smaller, more balanced and just plain easier to handle.
I won’t argue that the Canon 5DMK2 is a great still camera, and better than the GH1. But when it comes to real world video shooting and video quality, 5D, you’ve been served!