Optical advancements such as the then new coating technology pioneered during the Second World War made possible the advantageous splitting of groups into individual elements without the consequent penalty of excessive inter/intra element multiple internal reflections which lead to contrast loss. The 1953 Summicron introductory formulation is an example of Leica's early application of this technology to advantage. It is widely identified as a 7/4 (7 elements in 4 groups) because Leica identified it as such on its introduction. For example in G. Rogliatti's "Leica, The First 60 Years" it is described "With seven elements in four groups, this lens had (has) the characteristic that the front two pairs were (are) not cemented, but had (have) tiny "air lenses" between the glass elements." It should be argued that if you count the air spaces as "elements", then it is really a 9/4 (9 elements in 4 groups). More realistically, recognizing the splitting of the front two groups into four individual elements, it really should be counted as a 7/6 (7 elements in 6 groups).

The first embodiment of this lens formulation appeared first in 1953 and was applied, without any modification, in the following year to the M mount for the original M3.

A much less recognized new formulation appeared during 1957 when it appeared for all three of Leica's then current physical configurations: the screw mount; the rigid M mount; and the "BUG EYED" Dual Range Summicron. Leica, now taking a fuller advantage of the "air lenses" altered curvature and glass composition of the frontal split elements.

The third version of a Leica screw mount occurred in 1999 in a commemorative screw mount package which had the most modern (circa 1979) 6/4 fourth optical formulation.