Here's a test of the Samyang.
Vivitar is a marketing company which has never made any lenses. You can
possbily tell who made yours here.
<http://www.cameraquest.com/VivLensManuf.htm> Elsewhere on the site, 3
different Viv 35-105 lenses are shown, and that list is not complete in
other brand/models, so there could be another one or more. If yours is
made by Oly or Schneider (both highly unlikely) or Kino or Tokina, you
probably have a good to excellent lens.
>I'll also take the primes in addition this time, as i fear the Vivitar
>35-105 and the Samyang 18-28 ain't the greatest performers around. (No
>tests, just my impression)
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