A macro teleconverter is a special adapter lens added to a camera lens to increase magnification of a photographic subject. Macro lenses, when coupled with a digital single lens reflex camera (dSLR), achieve photographs of subjects at life-size in a 1:1 ratio; a macro teleconverter attached between the camera and the macro lens allows larger than life-size photography. Combining the two types of lenses allows closeup shots to be taken of tiny objects, such as wildflowers, insects on plants, and tiny underwater fish. Super-macro photography is the term used when teleconverters or extender tubes are added to macro lenses.
Unlike photography with standard telephoto lenses, macro lenses allow richly detailed closeup photography. Adding a macro teleconverter lens to a macro lens has its pros and cons. The additional lenses add more glass between the camera sensor and the subject, causing light reduction and some quality loss. These effects can be limited by the use of strobe lighting pulled in close to the camera ports. Using teleconverters does usually rule out being able to use autofocus on most cameras, though, even when they advertise otherwise.
Use of a teleconverter (TC) with a macro lens allows photographers an infinite focus. The TC doubles the working focal distance of a macro lens or can multiply its focal length. Attached to a macro lens, a TC will take the center portion of the frame and magnify it to fill the frame. Such lenses can attach to and work with most standard lenses, with some exceptions, although they work best with telephoto lenses.
Knowing how to attach a macro teleconverter to one or more macro lenses is crucial. A macro teleconverter must be attached to a quality resolution lens with higher magnification than the camera’s sensor in order to avoid loss of contrast in images. The TC should be attached to the master lens first; then, to avoid malfunctions, the coupled pair should be mounted on the body of the camera. The extender tube should be mounted between the teleconverter and the macro lens when using extender tubes to get more magnification. At these high magnifications, getting the focus just right, in the tiny depth of field, is critically difficult and important.