All you need to know about Close up lenses
All you need to know about Close up lenses | ||
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Close-up lenses come in two types. One kind is an actual lens designed for close-up photography and is used with cameras that have removable optics. However these lenses are usually referred to as macro lenses. When we talk about close-up lenses, we're usually talking about screw-on, filter-like accessories that attach to the front of your camera's prime lens. These add-ons are useful when you want to get even closer than your camera's design allows. Many digital cameras focus down to an inch or less. That's usually as close as you'll want to go, because if you get much closer than that, a three-dimensional object will be very difficult to light. There simply wouldn't be enough room between the lens and subject to allow decent lighting. An exception would be if you were photographing a transparent or translucent item, such as a transparency, but in most cases, being able to focus a few inches away is close enough. However, some vendors have a looser definition of close focusing, so you might happen to own a digital camera that allows getting no closer than a foot or two. Or, perhaps you own a fixed focus digital camera that offers acceptable sharpness for everything from a few feet to infinity. You, too, can take close-up pictures if you know the secret. You might have to choose your camera's macro setting, then set focus distance manually using a dial, but you'll still be able to take close-ups. Close-up lenses are generally labeled with their relative "strength" or magnification using a measure of optical strength called "diopter." A lens labeled "No. 1" would be a relatively mild close-up attachment; those labeled "No. 2" or "No. 3" would be relatively stronger. Close-up lenses are commonly available in magnifications from +1 diopter to +10 diopters. The actual way close-up magnification is calculated is entirely too complicated for the average photographer (unless formulas like Magnification at Infinity=Camera Focal Length/(1000/diopter strength) are your cup of tea) and not particularly useful. That's because the close focusing distance varies with the focal length of the lens and its unenhanced close focusing capabilities. However, as a rule of thumb, if your lens normally focuses to one meter (39.37 inches; a little more than three feet), a +1 diopter will let you focus down to one-half meter (about 20 inches); a +2 diopter to one-third meter (around 13 inches); a +3 diopter to one-quarter meter (about 9.8 inches); and so forth. A +10 diopter will take you all the way down to about 2 inches—and that's with the lens focused at infinity. If your digital camera's lens normally focuses closer than one meter, you'll be able to narrow the gap between you and your subject even more. In the real world, the practical solution is to purchase several close-up lenses (they cost roughly $20 each and can often be purchased in a set) so you'll have the right one for any particular photographic chore. You can combine several close-up lenses to get even closer (using, say, a +2 lens with a +3 lens to end up with +5), but avoid using more than two close-up lenses together. The toll on your sharpness will be too great with all those layers of glass. Plus, three lenses can easily be thick enough to vignette the corners of your image. | ||