Tuesday, December 18, 2012
Lenses For Still + Motion
Putting together the best optics for versatility and practicality
|This Article Features Photo Zoom|
|Why Not Zooms?|
|Affordable interchangeable lenses are one of the principal reasons why video-capable DSLRs achieved such popularity in the video and filmmaking community. Previously, camcorders with interchangeable lenses were a very expensive proposition at the same time that most affordable pro solutions offered only a single affixed zoom lens coupled with a smaller camcorder sensor. So zooms have application in video, but whether shooting for motion or stills, they're used more or less for one reason: convenience. This makes them a better choice for event coverage and wildlife while primes are the best option for most other aspects of videography and filmmaking.
Zooms are problematic for motion capture, as well. The zooming rings on a still lens are designed for a fast range of zoom to quickly track randomly moving subjects, so a slight turn equals a relatively massive change in angle of view. This makes zooming during a take difficult to perform smoothly unless you look at follow-focus systems with oversized gears for more gradual rotation of the lens. Follow-focus units and oversized lens gear rings almost always require a camera cage or rig of some kind to mount to the camera, as well. Zooms also need to be refocused if zooming in or out during a take, which is especially difficult to perform because focus is so difficult to achieve on the diminutive LCD screen of most DSLRs. The use of variable-aperture zooms also means changes to your exposure when zooming during a sequence. Zooming with motion is extremely prone to vibrations and subtle movements, as well, and for these reasons professional cinematographers often employ stabilization systems, sliders, rails, jibs and even cranes for moving a camera over choosing to zoom with a lens.
Choosing Your Kit
For DSLR filmmakers, the system you decide on is probably going to mch your camera system, but you should take into consideration several factors. The first is imaging quality. The best glass will provide the best resolution and color fidelity, and you shouldn't skimp on getting the best lens you can afford. Secondly, a lens set should have the same relative imaging quality across the board so the visual characteristics of footage matches between shots. Cinematographers tend to prefer that the lenses handle the same with similar torque and barrel rotation so they don't have to relearn a lens every time they make a lens swap. The same-sized front diameter is also an important consideration when using threaded filters across the line, especially since step-up rings can cause vignetting.
The system doesn't have to match the camera, however. Most video work is done with manual focusing, and though you often lose automatic functions, there are numerous adapters available for converting lens mounts from different manufacturers. Options include manual Nikon F-mount lenses on Canon cameras, cinematic Zeiss and PL-mount lenses on DSLR mounts and many more. Used lenses are available on the Internet, and it's also an option to rent, as cinematic lenses, even older models, are quite expensive.
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