I had a
Vivitar Series 1 70-200mm (version 3 with "A" setting) that was a great lens as well as the Samyang 18-28mm for my old Canon AE-1, AV-1 & F-1 cameras.
Both lenses are cheap third party lenses rivals OEM lens manufactures at center but slightly softer in the corner with a bit higher light fall off (which isn't a big concern IMHO). However, both lenses produced a bit more flares and distortion than OEM lenses (flares can be control by lens hood, and distortions can be corrected with today software).
If I recalled correctly the Vivitar 70-200mm produced sharper image as well as better colour than my old Canon 100-300mm f/4.5-5.6 USM lens.