Using Close-Up Lenses for Macro Photography
One alternative to buying a macro lens is the less financially cumbersome close-up lense. Close-up lenses are basically magnifying glasses that you attach to your normal lenses in order to capture a more detailed image.
How a Close-Up Lens Works
A close-up lens is a single or dual element ring that you can screw onto the front of your normal lens. There are many different qualities of close-up lenses, but none will ever be as crisp and pristine as a true macro lens. The glass acts as a diopter on top of your normal lens much like a magnifying glass does in front of your eye. So your subject becomes much bigger in the frame than it was before. Additionally, adding the close-up lens to your setup allows you to move your camera closer to the subject because it decreases the minimum focus distance. Thus, you can capture an even tighter shot than your normal lens would have previously allowed. Furthermore, you can stack a few close-up lenses on top of one another to get extremely close. But do not get too carried away, taking them on and off between shots can get impeding.
Quality of Close-Up Lenses
As previously mentioned, close-up lenses are not the high quality option in the macro world. This option is not meant to replace macro lenses, just provide a cheaper alternative. Generally, the close-up lenses with two glass elements are much nicer than those with a single glass element. The single element versions are much more prone to reducing sharpness in the image and causing chromatic aberrations. These effects can be reduced by using a smaller aperture. Try to keep your F-stop around an F16 in order to keep the negative side effects to a minimum. But the complications are not over yet.
Adding a close-up lens to your set up will not in and of itself affect your exposure. However, do not forget about the inherent light loss that happens in normal lenses and close-up photography. With the aperture so small and the lens fully extended to minimum focus, lots of light is left to bounce around inside the barrel and cause diffraction. This leads to a reduction in sharpness. Additionally, your lens will not be able to compensate for the amount of light lost as true macro lenses do. When your meter tells you to expose at an F22, you may need to compensate as much as 2 stops to account for the light loss. The specific details on how much to adjust your aperture can be found in Kodak's Photo Guide. Though this is not due to your close-up lens, it is important to keep in mind while you are shooting with it.
Close-up lenses are useful tools that you can easily carry around with you to get tighter shots on your normal lens. However, they are not perfect and do not eliminate the problems that come with trying to short cut around true macro lenses.Popular Lenses: