Mr. Jun Hirakawa(平川純) is a Japanese lens designer best known for creating the Pentax FA 43mm Limited and FA 77mm Limited lenses during his time at Pentax.[1]
Hirakawa said at the time that he regretted his "early retirement" from Pentax in 2010, around the time that Hoya acquired the company, and was subsequently hired by Tamron.[2]
^US patent 7317581, Ito, Takayuki & Hirakawa, Jun, "Fisheye lens system and a fisheye zoom lens system", published 2008-01-08, issued 2008-01-08, assigned to Pentax Corp.
Glass: AL (aspheric lens) - ED (extra low dispersion lens)
Coating: smc (super multi coating) - HD (high definition coating)
Sealing: WR (weather resistant) - DA* (lens is sealed) - AW (All Weather)
Features: PZ (Power Zoom) - QS (Quick Shift, most DA & all D FA lenses) - RE (retractable lens barrel) - digital aperture control (with PLM lenses on KAF4)) - IF (Internal focusing)