I was shooting a wedding tonight and I borrowed the photographers nikon 24-70 and used it with my speed booster,it had a very slight vinette that you ALMOST couldnt see I liked the effect. I was thinking of picking one up till I saw the were $1800 I wonder is the other brands would give the same effect.

Why not get one like this instead?
Nikon Zoom Nikkor 28 70 mm F 2 8 AF s D Lens | eBay (http://www.ebay.com/itm/Nikon-Zoom-Nikkor-28-70-mm-F-2-8-AF-S-D-Lens-/141467905754?pt=Camera_Lenses&hash=item20f024eeda)
There are more to be found on ebay below 1K

not sure what the difference would be but i use the Tamron 24-70mm f/2.8 DI VC (But of course the EF Mount) - Here is the Nikon Mount http://www.amazon.com/Tamron-24-70mm-Nikon-Mount-Model/dp/B007RZB3KM/ref=sr_1_2?ie=UTF8&qid=1416196606&sr=8-2&keywords=tamron+24-70mm+f%2F2.8

The nikon lens I linked to is fully manual if you use it with an adapter, so manual focus and iris but you have the advantage of adjusting the iris on the lens itself.

Might just get that one thanks!