Olympus introduced its own optical computational metrics by proprietary computer in mid-1973 and began the task of creating the retro-focus inverted 6E/5G optic of the XA, released in July of 1975. The design of that camera was evidently unorthodox, and the compromises that had to be made to fit a very sharp lens into a small space were formidable for that time (the question asked is, who else did the same thing, eliminating just about all of the sever forms of distortion and aberration, AND which wasn't a fold-out design?), though commonplace today (and often better) in many RFs.