The DSLR as a Video Camera
Or: Reasons Why the DSLR is no longer a tool for professional filmmaking
A few years ago, the DSLR came into fashion as a filmmaking tool for one very simple reason: it was the only way one could get the look of a large sensor cinema camera without breaking the bank.
What is the "look" of a large sensor? Traditionally, cinema was shot on 35mm film, most popularly with super35 format cameras that run the film vertically through the gate, producing an image on the film about 24x18mm. (This is smaller than the full-frame 36x24mm frame size of a 35mm still camera which runs the film horizontally through the gate.) The large image area of the "sensor" (film plane) creates a "look" which is mostly characterized by the shallow depth-of-field it achieves. Shallow depth-of-field is favored by portrait photographers for making the subject's face sharp against a soft background, and in cinema it can do the same thing, keeping the background from distracting the audience from an actor's performance in the foreground.
Traditionally, video cameras--even professional models--use sensors considerably smaller than super35 dimensions (between 1/4" and 2/3" measured diagonally) and as a result have quite a bit more depth-of-field. This isn't a bad thing. If you are shooting news, documentary or wildlife where things move quickly, you have a lot better chance of producing images that are in focus when you have a little more wiggle room in your depth-of-field. Small sensors have a lot of good things going for them.
When the DSLR started producing decent quality video from a large sensor, it was a revelation to low budget cinema--being able to achieve the look of shallow depth-of-field film cameras without the expense of film or a high-end digital cinema camera. But it came with many drawbacks:
1. DSLRs have crappy audio interfaces, audio controls and audio quality. Audio needed to be handled separately. (Very film-like indeed!) You can work around it, but it's a pain.
2. DSLR zoom lenses are not par-focal. That means that the focus plane changes as you zoom them. Zoom in, focus on your subject, zoom out, the subject is now out of focus. They aren't cinema lenses. You can work around it, but it's a pain.
3. The DSLR has awkward ergonomics for video. Again, you can work around it, but it's a pain.
4. DSLRs have sensors designed for still photos, with 16+ megapixels. The problem with this is that the processing power required to "downsample" that many pixels into HD video (2 megapixels) or even 4K video (8 megapixels) is simply not there. So the trick to making it easier is to "line skip" when reading out the pixels from the sensor for each frame of video. This is equivalent to looking at something through a screen door. It introduces a significant amount of moiré and aliasing artifacts in fine detail that can be quite objectionable. Ironically, this issue has become worse as DSLRs have become "better" with more pixels on the sensor. Earlier DSLRs with fewer pixels actually produced better video than many of the ones available now.
So why am I on this rant? For several years now there have been numerous reasonably-priced large sensor cinema (i.e. video!) cameras on the market that address all the shortcomings of the DSLR (audio, ergonomics, aliasing, etc.). There is just no reason to mess around with the DSLR as a filmmaking tool anymore. The Sony NEX FS100 and Panasonic AF100 (for HD) or the new Sony FS7 (for 4K) are simply astonishing digital cinema cameras at extremely reasonable prices with sensors designed for video. They produce incredibly clean, moiré-free shallow depth-of-field images with XLR audio inputs, cinema camera form-factor, and lens mounts for any lens you want to put on them. With cameras like this available, why on Earth would anyone screw around with DSLR video anymore?
A few words about underwater DSLR video
It often seems like the video camera has died in underwater video for anyone but the very top level professional underwater cinematographer. Amateurs are now happy to shoot video with a GoPro or the video mode on their point and shoot. Pros have switched to the RED, the Sony F55 or perhaps the PMW-200 or Z100 pro camcorders, depending on what they are shooting. (Television production prefers the zoom lenses and all around functionality of camcorders, cinema favors the RAW workflow of RED and F55). What has happened is that the "advanced amateur" video shooter has become an endangered species. This has left divers interested in video above the GoPro level with few choices for cameras or housings. As a result, the camera systems that have stepped in to fill the void are...you guessed it...DSLRs. And I think you know where I'm going now:
A few reasons DSLRs make even worse underwater video cameras than cinema cameras.
- A large sensor on an underwater camera is great for light gathering but extremely hard to get in focus. Depth of field is working against you here. When you see your work on a large monitor, you will be shocked how much of it is totally out of focus.
- One of the greatest gifts of underwater video cameras is the URPRO "flip filter" to selectively add or remove filtration for natural light white balancing. There is no substitute for it. Even the RAW workflow of a RED or F55 will not "fix it in post" except at depths less than about 30 feet. On a DSLR? Forget it. I have yet to see a DSLR housing that offers this feature. Without it I'm sorry, you are not working with a professional tool set.
- Dedicated video cameras have parfocal zooms with macro. You can shoot everything from a nudibranch to a whale shark with the same rig on the same dive. Try that with a DSLR.
- Image stabilization. Some of the Sony and Canon DSLRs now have image stabilizing lenses that work in video mode, but for the most part, it's really hard to hold a DSLR housing still enough to shoot professional looking video with one. Dedicated video cameras have had this feature for 20 years and it really helps underwater.
Can you get decent underwater video from a DSLR? Sure, sometimes. If you are shooting silhouettes or other video where color isn't that important (or you have some big lights on the rig), and there isn't a lot of fine detail that will suffer from aliasing and moiré, it may look fine. But in the vast majority of situations, a video camera in a proper video housing will produce a superior image.
The only argument for a DSLR as an underwater video camera that makes any sense is for the person who is primarily a still photographer who wants to occasionally shoot a little video. Just realize that under most circumstances, the video is not going to look as good as video made by a video camera.
What's the solution? There are still a few "advanced amateur" video cameras being made (such as the outstanding Sony AX100). If you really want to shoot decent video, think seriously about a dedicated video camera.
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