I need a wide angle plus a low apeture!

[KmH]

Nevermind very excited just learned its called bokeh and youtube has lots of tutorials!

I hate to pop your bubble but it's called depth-of-field (DOF), though many improperly call it bokeh. You need a wide aperture, not a low aperture.

FWIW, f/1.8 is a bigger number than f/4 is, because the lens f-number is a fraction.

Boken is not adjustable, while DOF is. DOF is controlled by 4 factors: focal point to camera distance, lens focal length, lens aperture, and focal point to background distance.

The technical expression of bokeh is the Circle of Confusion (CoC) a lens design produces. Like kundalini mentioned the number and shape of the lens aperture blades has a big influence on the CoC a lens produces.
Circle of confusion - Wikipedia, the free encyclopedia

 

[penfolderoldo]

As the 2 shoots you mention are so different, there's no way to get the effect you want with a single lens, so for the office / indoor scene the Tokina's probably a decent option (bearing in mind it's effectively a 16-24 taking into account the crop factor). For the engagement i'd go for something simple like the Nikon 50 1.8G (equivelant to a 75mm FoV) which would give you a nice result.

 

[The_Traveler]

Please assure us you aren't charging for this.