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Gear and Now: Focal Points
Posted Sep 8, 2004 - March 1998 [Volume 7, Issue 3] Issue Print Version     Page 1of 2 next »
  

Some of the best movie effects are the simplest ones. Merely zooming in to catch the surprised look of a loved one, or the pulling back to the wide shot that encompasses the entire scene can make the difference between a good video and a great video.


Getting the perfect shot sometimes requires more than just luck. That's why in this edition of Gear and Now we discuss zoom, wide-angle, and anamorphic lenses. First we touch on how they work, and then we look at specifications of one of each type of lens from three leading manufacturers: Canon, Panasonic, and Sony.

A Closer Look
A zoom lens works by changing the focal length, or distance, between the lens and the recording media. In order to zoom in, the focal length must be increased. To zoom out, it must be decreased. The zoom ratio tells you a lens' capabilities: The first number in the ratio represents the minimum focal length, the second number tells you its highest zoom factor. For example, a 12X10 zoom lens would have a minimum focal length of 12mm with a 10:1 ratio, for a maximum focal length of 120mm.

The f/stop value is also a ratio, with the diameter of the aperture of the lens in the numerator and the focal length of that lens in the denominator. It basically tells you how much light falls onto the recording media every time the shutter is opened. For example, an f/2, 30mm lens will have an aperture with a 15mm diameter and will let in a circle of light with an area of about 176.7mm squared. The more light you let in at a time, the more information you get to the filmed or recorded image.

Wide Shot, Short Film
In order to capture a 16:9 image without any special lens, a camcorder that doesn't have native 16:9 capability will crop the original picture on the top and bottom, creating the black bars that appear when watching a widescreen movie on a 4:3 ratio television. With an anamorphic lens, no cropping takes place. The lens instead contracts the picture horizontally so the frame image looks tall and thin. When projected onto a 16:9 screen, the image is stretched back out to the original size. This not only saves memory by not recording black bars, but the pixels that were used for those black bars can now be used to record the picture. The cameraperson can capture more of the original image in a higher quality.

A wide-angle lens achieves a similar effect, but is used in different applications. While the anamorphic lens is used to create a 16:9 ratio on 4:3 film without loss of memory, the wide-angle lens allows the shooter to view more of the background in a close-up shot. The wide-angle lens shrinks the subject, but retains the 4:3 ratio. The lens is short in depth and bulges in the middle. This allows a wider vertical and horizontal range of light beams that hit the lens to be bent so they create an image on the film or tape. A lens with less depth and more bulge will produce a wider angle than a lens with greater depth and less bulge.

The Lenses
For the purpose of this article, we looked at several lenses designed for pro and prosumer camcorders from Canon, Panasonic, and Sony that are widely used in videography work. Specifically, we targeted lenses in each category created as add-ons to Canon's XL and GL lines, Panasonic's AGP-DVX100 line, and Sony's DCR-VX2000 and 2100 and DSR-PD170. The following are some sample compatible lenses and their specs, which should give you an idea of what lenses are available for the cameras you use, what they cost, and what their capabilities are.

The Long View
These are only a couple of the lenses available for resale. When choosing which lens to buy or to use in a particular project, think about for the circumstances of your shoot. How far away will your subject be? How much of the background do you want in the shot? Do you have a large group of people or just a few?

All these factors come into play when determining what width of wide angle or anamorphic lens to buy, or what zoom ratio the zoom lens should have. Along with these factors, don't disregard the weight these items add to your camera, and that without a monopod or any additional stabilization devices, you'll be carrying the equipment through the duration of your shoot. If the lens is too heavy, too light, or doesn't feel right in your hand, your shots are probably not going to turn out as well.

(For more detailed specs on the lenses mentioned here, see "Lenses by the Numbers," next page.)



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