DSLR’s, the game-changing family of hybrid cameras are the darlings of the media world. Cheap and capable of eye-catching imagery, they’ve captured the imagination of thousands of would-be (and real life) cinematographers and directors. It seems everyone has a feature in production using the neat little cams which are going to take over Hollywood. But this picture isn’t perfect. Here are 8 reasons not to buy a DSLR for video.
1) Ergonomics – DSLR’s are still cameras first and foremost. Actually, DSLR’s are nothing but still cameras which happen to have a motion mode that makes beautiful HD video. They are in no way designed to shoot films. Too light, too small, awkwardly placed screen and controls, and missing handles and buttons make their use awkward and difficult impacting the video they shoot. To get around these limitations, companies and crafty individuals have constructed rigs, bordering on the insane, in order to simply make the device easier to use. Companies like Zacuto, Redrock Micro, and Cinevate sell kits that can end up costing more than the camera itself just to make shooting not a huge pain in the ass – an important fact to remember when pondering a new camera body purchase.
2) Moire and Aliasing – The worst problem you’ve never heard of, aliasing and moire can forever ruin a shot beyond the repair of even the most expensive post work. The Canon DSLR’s like the 7D and 5D Mark II are photo cameras with enormous sensors. They shoot 18MP and 21MP still photographs, far more than the 2MP needed for 1080p video. So, to save processing power and aid compression speed, Canon skips lines when capturing video. While no one knows for certain, it seems that only one in every 3 lines is kept. Each one of these lines is then compressed horizontally and finally recombined into the final frame. Samus can illustrate:
This recombination intensifies natural irregularities caused by the sensor intensifying moiré and aliasing. This clip highlights the problem extremely well.
It should be noted, however, that this problem is not unique to DSLR’s and can be found in all digital cameras. This is why it is common practice for news crews and documentary filmmakers to request interviewees not to wear striped clothing as it brings out the flaw. The image below is taken from a short film shot on a Sony CineAlta F900, an $80,000 camera, though the effect is especially noticeable in DSLR’s.
Beyond the line problem, moire can also crop up as distracting discoloration. For the Canon DSLR’s, when fine horizontal details are present, the sensor reacts in an entirely different and unwanted manner: colored aliasing.
The above screenshot is taken from Philip Bloom’s piece Salton Sea Beach filmed on a Canon T2i/550d (in case you thought their latest camera solved these problems). Distinct, multicolored artifacts disrupt the fine horizontal detail, a result of Canon’s line skipping.
These problems can be bad and easily ruin shots if you aren’t constantly conscious of this weakness of the DSLR’s. In fact, BBC has decided the problem is bad enough, along with some other factors, that they refuse to accept any footage shot on DSLR’s for their airwaves. This is an important fact for professional users looking to purchase a new camera for their work. There are filters made to help reduce these problems, but they do little more than soften the image (the other fix is purposefully softening the focus) in addition to costing quite a bit and working for only specific apertures and millimeters.
3) Shutter Rolling – The most visible flaw of the DSLR’s, rolling shutter is a byproduct of their massive sensors and photo-centric design. Imagine the camera’s sensor as a flatbed scanner or a copier machine. The entire sensor can image (this is the glass you place the paper on), but only a small portion of the information is recorded at any time (the bright, slow moving light on a copier). Since this reading does not occur across the entire sensor at once, instantly, like in a CCD chip, instead scanning across the sensor, like your copier, fast moving objects can be in different places during the same frame. The effect is a skewing where the ends of the objects are leaning in different directions because of their different positions during that single frame.
The Nikon D90 is the king of this jello world.
This problem affects all cameras with CMOS chips but is dealt with more effectively in video specific cameras which use faster polling rates and internal software to counter the problem.
4) Resolution – It’s a dirty secret that cameras don’t actually shoot the resolution they advertise. The Canon DSLR’s and the Panasonic GH1 are all capable of 1080p or 1.9K, the Nikon DSLR’s shooting 720p or 1.2K resolution meaning their outputted files are 1920?1080 or 1280?720 respectively. The actual measured resolving power in these frames is less, how much less depends on who you ask and what test they perform. I’ve seen some people on REDuser claim the Canon 5D and 7D are only capapble of about .8K or just slightly above standard definition. Another DSLR owner with a resolution chart claims 1.2K. The test with the most scientific validity (probably, though bias may be questioned) comes from RED which happily reports the Canon 5D gathers only 1.4K compared to the 3.7K – 4K of their own sensors.
The Canon 5DM2 is in black, the RED Mysterium X in red. Resolution is lost when the line loses it’s consistent wave form. To compare, the Sony F35 measures at 1.7K, 35mm ASA 100 from a 4K scan 3.2K, and 35mm ASA 500 from a 4K scan 2.8K.
5) Compression – The Canon DSLR’s record to a lossy H.264 4:2:0 format. The bitrate varies from camera to camera but is approximately 48mbps which is a greater data rate than HDV and AVCHD but offers a similar (and some would argue poorer) compression. Even with all this data, there is still a lot of compression exacerbating existing aliasing and moire problems in addition to your everyday jaggies. Furthermore, the codec is very poor for editing natively and requires a recompression for all but the newest editing computers. For Final Cut Pro users, Canon has released a plugin to simplify this process, but for the rest of us, your only real option is to purchase Cineform Neoscene for $100 to generate an editable file (Cineform also extrapolates missing data to create a 4:2:2 10-bit file).
Unfortunately, the HDMI output, which would be the normal workaround to avoid compression, is either not HD or carries burnt on screen information on all Canon DSLR’s. There are constant rumors of a 4:2:2 raw solution in the works, but nothing has (or likely will) materialized.
6) Audio – DSLR audio is completely, 100% useless. Some are mono, others are stereo, all are terrible. If you are using a DSLR for filmmaking, documentary work, live events, or anything that needs decent sound at all, you MUST use an external recorder. Here, let me show you.
The reason for this is the poor quality of the built in microphone, the poor quality of the preamp, and the inclusion of auto gain control on all canon DSLR’s (except for the 5D Mark II under the new firmware). The AGC has the added effect of making external 1/8? plug microphones like the Rode Video Mic essentially useless as well.
Consequently, most DSLR filmmakers have turned to the Zoom H4n, a small portable audio recorder with built in stereo microphones and dual phantom powered XLR plugs. The zoom retails for $299, an otherwise hidden cost for a filmmaking oriented DSLR purchase.
7) Still Photo Lenses – The current generation of still photography lenses are the most technologically advanced optics to have ever been created. They have built in image stabilization, amazing electronic apertures, instant auto focus motors, and other neat photographic features. Unfortunately, many of these features are a hindrance to video. Image stabilization is loud and useless on a tripod actually adding motion. Electronic apertures limit the number of stops. Instant auto focus motors mean there is no direct focus manipulation making hitting marks difficult and inconsistent as there exists a “float” in the magnetic positioning. Furthermore, the rotation of still photo focus barrels is generally small to allow faster focusing which makes pulling focus for video far more difficult.
Lens purchases can add up quickly and good lenses can cost as much and more (especially if you have a T2i/550d) than your camera body. Photographers will tell you to invest in glass not bodies but this is a foreign concept to video people who are used to making a single purchase and shooting (except for the very high end). Lens lust will quickly drain the money you need for other mandatory accessories for shooting and is a common disease of new DSLR owners.
8 ) Record Limits – For the live guys and interviewers, the 12 minute record limit of the Canon DSLR’s could be a deal breaker. This means no seamless one camera weddings (and if you’re trying that you should be ashamed), no one shot play recordings, interrupting talent during longer interviews, and a multitude of other problems. For the filmmaker, this shouldn’t be much of a problem unless you’re working towards Russian Ark.
Concluding – The problems faced by DSLR’s are varied affecting image, sound, organization, and more. Some of the problems are trivial, others are easily solved (though perhaps not cheaply solved), and some are without any foreseeable solutions. Still, the cameras possess the enormously redeeming values of a 35mm sensor and a rock bottom price, a topic I will expound upon in the very near future with the counter of this piece.
I bought a Canon 7D and I love it. I’m shooting more now than I ever have and I’m constantly impressed with the quality of the image, pixel peeping aside. All cameras are nothing more than tools making it possible to share what you have in your head. Some give easier paths to that goal than others, but no camera ever made a director or a photographer or a cinematographer. Don’t get hung up on your gear and instead go out and shoot.