Vivitar 85mm F1.8 Specifications
analog/digital limited (dumb mount - aperture priority or manual modes only)
Diagonal Angle of View:
Number of Aperture Blades:
internal focus mechanism, manual focus only
thread mounted, round shape
Aperture settings are limited to 2.5, 3.2, 4.0, 5.0, 7.0, 11.0 and 22.0 (nothing in between).
The Opteka is reported to be of rather cheap quality (chromatic abberation/purple fringe, bad bokeh and stuck apertures after few times in use).