Center focus Porro prism binoculars go way back almost to when Zeiss marketed the 1st Porro prism binoculars in 1894: In 1898 Goerz offered 3X, 6X, 9X and 12X Porro prism Trieder model binoculars all CF and also very popular at the time; in 1910 Zeiss introduced the CF 6X21 Telexem and hugely popular 6X30 Silvarem which was made until 1975; Leitz was selling several CF models at least as early as 1912; I don't have the years but Ross was also making CF Porro prism binocular in the very early 1900's and probably in the late 1890's. Quite a few of the old CF Ross appear for sale today indicating they were popular in their day since a lot seem to have been made.I was really wondering when center focus became really popular in Porro Prism binoculars. I can remember a Biology Professor when I went to college about 50 years ago complaining about how useless IF binoculars were for use in Zoology. Apparently they were still commonly used then.
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