Normally they tell you to double the focal length of a lens that you use with a 35mm camera to get what you want with a 6x7 camera. Of course this is an approximation. Also a 6x7 camera's viewfinder and negative are more square than a 35mm camera's so it will still look a bit different. I used a 180mm for tight portraiture on my Mamiya RZ67. It had the same depth of field as my 180mm lens on my Contax 35mm camera. Of couse it had less depth of field than the 100mm that I used for tight portraiture with my Contax.
Originally Posted by colonel
I'm no lens expert but from my understanding, Bokeh is determined by the lens aperture. The more aperture blades a lens has, the more circular the aperture. Lenses with great Bokeh have a very circular aperture.