The lenses for the RB67 system can be divided into five series:

The Mamiya-Sekor Non-C series - the first generation, single-coated, released along with the RB67 Professional in 1970;

The Mamiya-Sekor NB series - the transition series produced in 1973-1974, optically identical to the Non-C series but with a new barrel design that matched the later C series;

The Mamiya-Sekor C series - the second generation, multi-coated, released with the RB67 Professional S in 1974;

Design emphasis was placed on high resolving power and excellent color balance justifying the 6x7cm format. A multi-coating process made the Mamiya-Sekor lenses among the sharpest in the world. It eliminated reflection over a wide range of frequencies, making images clearer and tones crystal clear. In color work this was especially valuable as color rendition was vastly improved.