Can DSLR cameras with HD video recording be used for professional video production?
by Joe Gambaretto
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Image Processing: Still image vs. motion picture
    Although the CMOS sensors of the last few years have had the necessary pixel resolution (more than enough, as noted), it hasn't been a given that meant recording HD video was possible. It is one thing to capture one high-rez picture from a split second exposure. It is another thing to capture and process a continuous stream of frames at 30fps. The processing power required for video is higher than for still frames, even with a lower resolution than the CMOS imager is capable of. And speaking of that, to record HD video, a down conversion process is required. The full frame is resampled to 1920x1080, 30 times a second. With earlier processors, the horsepower just wasn't there. And both the sensor and processor have to work extra hard to perform the continous capture and down conversion, which can cause extreme heat build up, which could quickly shut down or damage both components!
     But as has happened in the world of computing and camcorders designed for these kinds of workloads improving over the years, so of course have the components used in higher-end still frame digital cameras. The various manufacturers offering HD from still image based units have worked out these issues in the sensors, processors and firmware/software, and have chosen various methods of HD video compression schemes to handle the differences of motion pictures vs. still frames.

Data Storage requirements
     As we have seen in all areas of video production over the last decade or more, data storage size, speed and reliability are also factors in recording HD video from DSLR cameras.
     And, just as the moves through hard drive recording systems for digital video have developed somewhat slowly, and are shifting to solid-state storage with no moving parts, the same has been true for still image cameras. The size and read/write capabilities of each cameras' data storage system are of course factors in the progression to HD video capabilities in DSLR (and non-DSLR) cameras. None of the DSLR cameras offering HD video have opted to graft on a tape-based recording system for perhaps obvious reasons, so solid-state storage such as compact flash (CF) cards was a serious road block on the path to motion picture capabilities.
     And even with increased capacity and speed of solid state storage, our example camera, the Canon EOS 7D is limited to approximately 12 minutes of recording in HD mode on a 4 GB CF. While this length is no stranger to those who have shot 16 or 35mm motion pictures, it can come as a surprise to those used to tape-based camcorders with 60 minute plus capacities. The obvious solution is to have more than one 4GB CF on hand if you need to shoot more than 12 minutes of footage (which is usually the case on most shoots). While a well planned shoot for a 30 second basic TV spot commercial might fit on one card, the reality is multiple takes from talent, required actions, etc.

Next: The DSLR form factor's impact on pro video shooting


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