Digital Video - December 2008 - (Page 34)

DV 101 BY JAY HOLBEN THROUGH THE LOOKING GLASS LENS ADAPTERS CAN GREATLY EXTEND THE MAGIC OF YOUR CURRENT OPTICS. A lthough relatively small-sized camcorders, especially of the HDV variety, have allowed more videographers entry into the HD arena, there are several trade-offs to smaller chip sizes. One of them is the wide-angle shot, as the smaller imagers of 1⁄3" (and smaller) cameras make it increasingly difficult to inexpensively manufacture quality lenses, especially with wide angles of view. ANGLE OF VIEW The angle of view (AOV), or field of view, describes the degree of view a particular lens is capable of. A 180-degree AOV would see everything perpendicular to the lens, including the edges of the lens itself! Years ago, when I was first teaching myself photography, I sat on the floor of my mother’s living room with a 35mm SLR, a roll of masking tape, two plastic cups, a tape measure and a protractor. The AOVs I was reading about just didn’t seem right to me, and I wanted to see if they related to real-world optics. I set the camera down on the floor and carefully positioned each plastic cup at exactly the same distance from the lens and moved them to the very extreme of the horizontal view from the camera. I then taped a line with the masking tape from each cup to the lens, thereby creating a large “V” angle on the floor. Using my trusty protractor (left over from high school geometry), I measured the angle of the tape V and — lo and behold — it matched the published angle of view for that focal length precisely. And that went a long way toward solidifying various lens sizes in my mind. Years later, I could look at a scene, imagine a framing and request a specific prime lens to match that perspective — and get pretty close about 90% of the time. Experience and experiments like this one helped develop those skills. Any lens has two angles of view: one for the horizontal plane and one for the vertical. For our purposes here, we’ll only look at horizontal AOVs. A WIDE ANGLE REVOLUTION IN A LIGHTWEIGHT COMPACT ASPHERIC CONVERTER INTRODUCING THE EX 0.75X ASPHERIC WIDE CONVERTER • Advanced aspheric technology reduces geometric distortion and chromatic aberrations and improves off-axis performance • Smaller & lighter than non-aspheric lenses • Delivers 25% greater angle of view • Maintains full zoom thru • Quick bayonet mount for Sony EX1/EX3 • Crafted with precision engineering for optimum performance MM IS MM — TARGET SIZE DEFINES AOV All focal lengths, no matter what the format, are optically the same. A 50mm lens for a 35mm motion picture camera has the same distance between the nodal point (roughly the center of the lens where the light rays converge) and the focal plane (film) as does a 50mm lens on a 1⁄6" consumer CCD camcorder. Modern zoom lenses, and primes with multiple elements, can cheat this physical distance to a degree, but the optical properties remain the same. In a 35mm motion picture camera, the diagonal of the frame aperture (Academy) is 1.07" — a pretty sizeable target on which to project a very wide angle of view. With a motion picture camera and a 12mm lens, which is very wide, you can have a field of view of 92.1 degrees without significant distortion. That same 12mm lens on a 1⁄3" CCD camera, which has a diagonal of .236 inches, will give you an angle of view of only 28 degrees! The smaller target for the lens gives a considerably narrower angle of view. www.dv.com LENS HOOD Retail Value For more details, see rebate form: www.16x9inc.com FREE $250 http://www.16x9inc.com http://www.16x9inc.com http://www.dv.com

Table of Contents Feed for the Digital Edition of Digital Video - December 2008

Digital Video - December 2008 Contents DV Expo Gallery First Look: Ultimate 35MM Lens Adapter Vidock GFX Pro Videostudio Pro X2 Instant Expert The Making of Roman Close-up: Dave Ruddick Crypto Camerawork Click To Play DV101 Production Diary

Digital Video - December 2008

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