My Sirius 18-28 doesn't sound as bad as this description of the Exacta ... below!
I think the Sirius is a very nice budget lens ... and am not disappointed with the results. It does vignette slightly at 18mm and produces darker slides below about 20mm (never could figure out why!) ... a tweak of +1/2 will correct it.
Cheers, Kyocera Kid.
"Hi Robert,
You are right, the "Exakta" lenses are the same as "Samyang" lenses.
I have had the 18-28 zoom for about 6 weeks, and shot a lot of pictures
with it, but I never got good results. I sold it and bought a 17mm Tokina,
a much better lens.
The Samyang and Exakta lenses are made in Korea (
, notice the "320kg" weight of the 500mm mirror lens....) and are sold
under a few brands. The built quality isn´t bad, the 18-28 zoom seems to
be a all metal construction, but with large tolerances: the front element
of the zoom could be shifted sidewards by about 1mm ! Sharpness was
acceptable when stopped down to f8, vignetting is high full open and
acceptable when stopped down. But what I really hate on this lens, are the
bad colours and very hard contrast. Pictures didn´t show fine structures
in darker areas and colour tends to blue-green. The Tokina however is
nearly "Zeiss"-like regarding contrast, sharpness and colour.
Save your money, don´t buy this zoom.
Dieter"