19-35mm Photodo, Dyxum accuracy and lens confusion?

[FilmFrenzy]

Just whiling away some time looking at MTF ratings for lenses I own on Photodo.
I was a bit curious to see that the Cosina 19-35 I recently bought as a stop gap for wide angle has a different and much better rating than the Vivitar 19-35 which according to Dyxum is the same lens.
Are they wrong? Could this just be lens variation? Are the Vivitars just knock offs of a Cosina design? Did Cosina manufacture the Vivitars to a lower standard than their own?

I'm also quite surprised how well this Cosina did in the tests. Looks like if I make sure I stop down (and I have a good copy), I might have a reasonably competent lens.

Has anyone any experience of using this lens on 35mm?

[bechisbest]

I had a Nikon fit Cosina, It was a good lens.

[sillyconguru]

Has anyone any experience of using this lens on 35mm?

I have the, Nikon fit, Vivitar badged version; it is almost as good as the Nikkor 18-35mm when used on a 6MP DSLR (especially when stopped down) according to my unscientific testing.

I've had a 30"x20" print produced, albeit by scanning a 10"x7" print (the print had extensive dodging/burning work applied in the darkroom, hence not scanning the negative) and interpolating, and the quality is totally acceptable (the original print looks superb).

I think that this is a great lens for its cost, it is just a pity that the build quality feels cheap.