I’ve had the Tokina AF 19-35mm for a few years now, and often see it on the internet that the Tamron/Promaster/Cosina/Phoenix/Vivitar lenses of the same focal length are all the same lens just rebranded. Looking at pictures individually, they look the same, all sell for similar peanuts price & I believed it. Based on this info and having seen mine, my dad snapped up a Vivitar S1 version a few years ago when offered for £40.
It’s then suddenly when you are graced with both in your hands you can see clearly they are not the same lens. For a start the Tokina is bigger and weights a good 50% more than the Vivitar, the Vivitar is noticeably cheap plastic, the Tokina, whilst not of more modern Tok 12-24 build quality, is better built than a lot of other cheap lenses I’ve handled (budget Sigmas, Canon kit lenses etc) and there is various construction differences. One of the first of these is that on the Tokina, the filter thead holder is fixed, and the lens zooms & focuses within (great for filter users), but on the Vivitar the lens & filter holder are the same unit and zoom together & it rotates during focusing (very bad for filter users).
It’s tricky to see on the pics, but on the Tokina you can just see where the lens centre is zoomed up 2mm above the filter holder which stays fixed. On the Vivitar the whole top section zomes/rotates together.
At the rear again you can see internal differences, but I’ve no idea of any difference this makes to actual pictures.
At some point in the future if I’m feeling mind numbingly bored, I’ll find do part 2 of the test & put them on my 5D and compare optical quality, however I’d recommend buying the Tokina over the others just for the improved build quality anyway, and I’m more tempted to test the Tokina vs the Canon 17-40 to see if it’s worth me upgrading. For now though I’m sticking with the Tokina, it cost me £65 4 years ago and it’s delivering shots like this on the Canon 5D (mk1)