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Tuesday, June 8, 2010

Behind The Scenes

The truth about HD video capture in DSLRs

This Article Features Photo Zoom

The PRIME II processor of the Pentax K-7, with high-definition video capture at 30 fps in 1280x720 (720p) and an unusual 1536x1024 (which is the 3:2 aspect ratio of the sensor, rather than the more common 16:9 widescreen format).
Canon’s video-capable DSLRs (including the original EOS 5D Mark II with the new firmware update 2.0.4) provide a choice of frame rates, except the EOS Rebel T1i, which offers 1080p video at a slowish 20 fps and lower-resolution video at 30 fps. Nikon’s HD DSLRs capture at 24 fps, and Pentax video DSLRs use 30 fps as does the Samsung NX10. These frame rates are a tad slower to match the NTSC/PAL format standard: 24 fps is really 23.976; 30 fps is 29.97; and 60 fps is 59.94. Some cameras also offer the European PAL rates of 25 and 50 fps (which really are 25 and 50 fps, respectively).

The Future
Interestingly, camcorders are making the move to incorporate DSLR sensors and interchangeable lenses into their construction. Now that still cameras are offering video, it’s hardly surprising that video companies are taking a long look at still cameras and figuring out how to incorporate their advantages in the designs of new camcorders. Two companies that have their toes in both the still and video market have already announced camcorders that will utilize sensors from their still camera lines.

The Panasonic AG-AF100 is using a Micro Four Thirds 16:9 MOS sensor, making it compatible with the 4/3-inch lenses, filters and adapters. Though there’s currently little information on it, Sony has teased a camcorder that will use the Exmor APS HD CMOS sensor and the new E-mount of its Alpha NEX-5 and NEX-3 mirrorless cameras. Though E-mount lenses are currently limited to two lenses, an 18-55mm ƒ/3.5-5.6 and a 16mm ƒ/2.8 (with a superzoom that covers a range of 18-200mm planned), the camcorder also will work with their Alpha mount series of lenses via an adapter. The mirrorless E-mount system itself is interesting in that it removes the mirror system of a DSLR while still providing an interchangeable-lens camera, similar in many respects to the Olympus Pen series. For video, removing the mirror also removes some of the disadvantages to video capture. All in all, it’s an exciting time for both still cameras and video camcorders.

Clip Limits
Canon HD DSLRs can record up to 4 GB of video at a time, which works out to approximately 12 minutes of HD or 24 minutes of SD video. Nikon and Pentax cameras can record clips of up to 2 GB in length, which results in about 5 minutes of HD or 20 minutes of SD. These limits are due to file format restrictions, not inherent camera limitations. From a practical standpoint, unless you’re doing a De Palma-esque tracking shot or shooting a documentary, clips rarely exceed that time anyway. Something to bear in mind, though, is that professional HD camcorders have sensors designed for extended use, as well as heat sinks that will remove the extraneous heat produced during such long exposures. The heat in a DSLR can build up during Live View use, increasing image noise. The cameras are designed to shut down before any permanent damage is caused, as well.

Camcorders are designed for video, with good eye-level viewfinders and external monitors, not to mention a form factor designed for handholding for long periods of time. DSLRs were designed for single shots or brief sequences, and the eye-level viewfinder in a DSLR blacks out during Live View operation because of the swinging mirror. This means that you’re holding the camera away from your eye in order to view the LCD monitor. Companies like Redrock Micro and Zacuto are already offering a host of modular rigs that solve these problems and more, however.


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