Digital Video Expo – DSLR Video
September 29, 2010, Digital Video Expo, Pasadena, CA– in a hardware session, Richard Harrington, CEO of RHEP pixel, Inc. talked about using a digital single lens reflex (DSLR) camera for creating video content. The first consideration is the body characteristics and available accessories. The imaging sensor resolution for still pictures a significantly higher than that required for video, so the emphasis should be placed on the interaction of lenses, equivalent F. stop, and equivalent ISO ratings for the cameras.
Some of the important accessories to consider include an external handgrip which provides an extra battery and an extra slot for a memory card, both of which can be hot swapped during filming. The extra hand grip also adds weight which helps stability, but it’s tiring to hold over a day’s shoot. The handgrip also supplies a platform for tripod mounting and accessory controls.
Combinations of frame rate and different resolutions are possible, because the cameras output highly compressed content. Some of the frame rates for various resolutions follow. A rate of 60 frames per second will output something appropriate for 720 HD. Frame rates of 30 or 24 frames per second are capable of full 1080p resolution. Camera manufacturers use different compression schemes with Nikon supporting JPEG and Canon supporting H.264.
The biggest problem in using the DSLR’s is they are designed for shooting single pictures, so are not well ergonomically designed for shooting extended sequences. In addition, the standard viewfinder and the LCD viewfinder do not have sufficient resolution for critical focus. Therefore, an external monitor with a hot shoe mount is necessary for any other video production.
Power for the cameras is always an issue, so users are advised to fully use the management firmware in the cameras and also have a dual charger per camera plugged into the wall to charge two batteries while filming. If electricity is not available on site, users should have for or five spare, fully charged batteries for each camera.
Always bring at least one set of spare cables (per camera) and have many spare memory cards available. Faster grade memory cards reduce total power consumption during the shoot. As noted above, the output is compressed so no RAW data is available. Motion JPEG, used by Leica and Nikon is an older compression standard and creates many artifacts.
Compression is used to trade image quality for recording time. One of the challenges in using DSLRs is that the recording length is limited in size due to a WinFAT 32 file sizes restriction of about 4 GB, or about 12 minutes of filming. A quick workaround is to use the stop start button to reset the timers. Therefore, it’s very important to plan breaks, have multiple cards on hand, and stagger coverage so there are no significant gaps in the recordings. External monitors are very important. Consumer grade monitors are fine for this application, since they use is similar to that of a casual home user. All the cameras do support pro-quality monitors through HDMI adapters.
Lenses are an essential ingredient in the production. The difference between OEM and third-party lenses is not significant for video. Image stabilization, in camera or in the lens, is not useful for video, because it interferes with natural camera motions. Lens characteristics like focal length and aperture reflect the normal considerations for lenses. Zoom lenses give greater flexibility at the cost of greater weight and lower image quality, while prime lenses are lighter, faster, and sharper. Always try to get the fastest lens possible in any configuration.
For shooting videos, lenses need to be cinematized. This removes the stops and enables focus pull, the ability to change focus as the object interest moves out of the original focal zone. If the lens is a zoom lens, it would also have obligations to the zoom control to allow manipulation via an external knob.
Other accessories are important for changing camera position. As a part of the setup process, users should get in the habit of logging the settings for shooting and image of a resolution chart prior to recording. This captures the metadata for the camera and all the other settings.
