This lens is recognized as the Finest lens ever created by Leica or any Manufacturer. As many manufacturers these days are throwing around the word APO in the marketing of their lenses, Leica takes this designation very seriously. The APO-Macro-Elmarit 100mm is corrected completely through the Infrared range, allowing you to shoot Infrared film without re-adjusting the lens focus. Therefore, Infrared markings on the lens have been done away with. The lens is characterized by evenness of field, absolute film sharpness from edge to edge and No Loss of quality when used wide open at F2.8. The color balance of the lens is perfectly neutral. The lens is somewhat large and heavy but is easy to handle and perfectly balanced on the SL or R body cameras. Flare reduction is top notch as the front element is deeply recessed within the lens barrel and the built in Hood allows convenient added protection against flare when you need it. The focusing mechanism is internal and as such, the front of the lens does not rotate allowing easy use of 60mm Polarizing filters. The lens focuses to 1/2 lifesize and to 1:1 (lifesize) with the optional Leica APO-Elpro Adapter for this lens. The minimum focusing distance is 45cm, allowing you ample room between yourself and subject. The lens was made in both R and ROM mounts. The std. R mount is no longer available, but Leica will convert this lens for use on the Leicaflex SL series cameras for a reasonable fee. Nothing wiggles or feels flimsy on this lens. It is the Landcruiser of lenses.