In conventional telephoto converters, a lens with a pronounced convex shape is used to refract the light received through the first element to a greater degree. This results in the desired reproduction ratio, however, chromatic aberration can occur. In the event that a convex ED lens is used, such chromatic aberration is corrected. However, the refractive limitations of such a lens make it difficult to reduce overall dimensions.The Nikon TC-E3PF 3x Phase Fresnel Telephoto Lens is based on the Phase Fresnel lens (pronounced Fray-nell) - a lens which appears to have a series of concentric circles engraved onto it and which has a jagged surface in cross section - the TC-E3PF is made possible by fusing two such lenses together, and it succeeds in correcting any chromatic aberration to the same high degree as an ED (Extra-low Dispersion) glass lens while simultaneously achieving a reduction in overall body length. As a result, the lens is significantly shorter and carrying it around becomes more convenient.