Despite recent experimental success in demonstrating negative refraction in and focusing by so-called left-handed materials, it may never be possible to realize "superlenses" with a diffraction limit of zero, as predicted by John B. Pendry of Imperial College London in 2000. That is the conclusion of scientists at Purdue University in West Lafayette, Ind., and at Massachusetts Institute of Technology in Cambridge, who have completed a mathematical analysis of semi-infinite and finite-thickness examples of these materials.According to their investigation of field-growth and power-dissipation metrics, left-handed materials have the potential to compensate to some degree for the effects of evanescent field decay in normal materials and thus improve focusing. However, any degree of loss, which is presumed to exist in left-handed media, will affect field growth, ruling out the possibility of perfect lensing.The scientists nevertheless point out that it remains feasible that left-handed materials could be used to produce better imaging systems than currently are possible with conventional media. A superlens may be an impossibility, but it remains to be seen exactly how close to perfect is achievable.