I need a cheap zoom lens for film making. HELP!

I picked up a used Tokina 28 - 70 F2.8 last week. I use it on a Nikon D7000 with good results but they come with a Canon mount too. Got it for under £130 which in my view is a bargain.

It seems a bit softer wide open (compared to my Nikon 50mm 1.8) but stopped down to 3.2 or 4 it gets very sharp.

Worth checking out if you can find one cheap.

EDIT: not many reviews around, but there's one from Ken Rockwell:

http://www.kenrockwell.com/tokina/28-70mm-f28.htm