http://www.dofmaster.com/dofjs.html will tell you, just input your distance and f-stop.

At 17mm, f2.8, you have

Subject distance 4 m

Depth of field
Near limit 2.3 m
Far limit 15.4 m

But zoom to 50mm f2.8, you get:

Subject distance 4 m

Depth of field
Near limit 3.69 m
Far limit 4.37 m


You can try different focal lengths and f-stops yourself...