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Basic Training: Zing Your Images

Basically, there are two types of lens adapters: ones that attach something (usually something glass) to the front of your camera and ones that attach your camera to the rear of something else. Isn't that the same thing? Yes, but not quite.

The most common lens "adapters" are really auxiliary lenses, technically called lens converters, that attach to the front of your camera. Typically, they magnify or reduce the image - either increasing the telephoto range of your lens or its wide-angle capacity. A 2x converter, for example, will double the focal length of your lens throughout the span of its zoom. A .7 converter will reduce your lens' focal length by 30% (multiply your focal length by .7), so a 100mm lens becomes a 70mm lens. These are commonly called "adapters," because they "adapt" to your camera by providing threads or a slip-on ring that will hold a lens a certain distance in front of your camera. Technically, speaking, however, the correct term for them is converter, as the lens converts the image optically.

This type of converter runs the gamut in price - typically, you get what you pay for. A $30 wide-angle converter gives you something in the area of $30 image quality, but it's often fun to play around with. Other auxiliary lenses, like those from Century Optics (owned by Schneider), may run from $600 to $3,000 and provide high-quality images.

Sanyo and Kodak also make inexpensive converters ranging from .45 to 2x. The image quality of these lenses varies widely. Things to look for are "coated optics," which keep diffraction at a minimum, and the number of elements in the lens. Typically, the more elements (lenses) you put together, the better your resulting image will be. This is because a single lens tends to magnify or reduce part of an image while distorting another part, so a second lens mates to the first, which corrects for some of that distortion. Numerous lenses connected together in groups can (and do) virtually eliminate distortion, but don't expect them to be cheap. Another thing to check is whether the converter is "zoom-through"- capable. This means that you can "zoom through" the converter without losing focus. This is handy if you plan to use the converter throughout a shoot.

Apart from putting a converter on your camera, you can also use an adapter to attach your camera to an object designed for another task. For example, Century Optics makes an adapter that will allow you to put Nikon film camera lenses on a Sony ½-inch CCD bayonet-mount video camera - if you have a desire to do that. More on why that might be useful later.

The Digi-T camcorder adapter for telescopes by ScopeTronics, which retails for about $30, is a series of step-up rings that will connect your camcorder to your telescope by using the threaded filter rings. You'll need to focus using your camcorder's external viewfinder, but this will have you well on your way to videotaping celestial events like eclipses. When turned to terrestrial uses, it's a stupefyingly powerful telephoto for documenting those eagles feeding their babies in the nest a half mile away. Using a type of image capture called "eyepiece projection," you will have the full magnification powers of your telescope at your disposal.

In the typical astro-photography process, light collects cumulatively on the CCD or film, meaning a long exposure will produce brighter images. Due to the very dim nature of most celestial objects, your video camera will be limited to the brighter objects in the sky - the sun, the moon and the planets. (Don't, by the way, point your telescope or your video camera at the sun without the proper filters in front of the primary lens element; you can damage both of them from the light and heat.)

The technology for connecting your camera to a microscope is the same as that used for connecting it to a telescope. Your camcorder needs to attach itself to either the microscope, or, using eyepiece projection, to the eyepiece. Eyepiece projection will get you higher magnification but will give you reduced image quality.

One major difference between 35mm film and video is the very shallow selective depth of field that's available in 35mm. This allows directors to isolate their subject in focus and have the background soft or completely out of focus. Because of its smaller sensor size, digital video doesn't have nearly the range of depth of field that 35mm does. This is often a dead giveaway that your production was shot on video, despite your clever usage of a 24p frame rate and the other hoops that videographers often jump through to get their final product to look film-like. Some clever moviemakers have discovered that you can build an adapter that connects your video camera to a rectangle of ground glass and then project onto that glass with a 35mm cinema or even a 35mm still photography lens, videotape that with your camera's macro function and get a remarkable film-like look. There are home-brew kits and instructions for do-it-yourselfers on the Web, or you can buy something like the M2 cinema lens adapter, which is about $2,300 for a complete package from Redrock Micro.