The original 35mm Summilux was by longevity measure Leica's single most successful modern generation lens. It was produced from its introduction in 1961 for 32 years until it was superceeded in 1994 by Leica's second generation 35mm "Aspherical" the 1.4/35 Summilux-M ASPH. The original 35mm was first co produced along side the "Aspherical" 35mm Summilux as a less expensive alternative until the "ASPH" 35mm Summilux, which had profound production economies, was introduced at a more competitive price. [BTW, the two designs, covered elsewhere on this site) are similar but by no means identical and there is a hot debate as to whether the "Aspherical" design is actually superior to the "ASPH" and it does command an approximately 25% to 35% premium over its successor in the used or secondary marketplace.]

Introduced in 1961 for the M system, it was the very first credible popular 35mm focal length f1.4 lens. SLR retrofocus designs had not yet progressed to the point where decent available light designs were happening. Nikon best to that date was a 35mm f1.8 for its rangefinder bodies (though it was known to have an f1.4 design in development) and it as well as other camera/lens companies were still struggling to come up with decent 35mm f2.8 SLR designs. Nikon's 35mm f1.4 was not to arrive for 10 more years and though it employed "CRC" floating elements for corrections to render a much larger reproduction ratio range, it was not at all as sharp as Leica's much older design 35mm f1.4.