Nikon Manual Focus

Nikon description: Matte/Fresnel field with 5mm and 12mm diameter concentric reference circles. The reference circles are there, presumably, to denote where the centerweighted metering’s emphasis is. Incidentally, the Photomic Tn finder was the one that established Nikon’s now-traditional 60/40 split (which varies up to 80/20 on the F3).