Thanyou,I now understand the variance between full frame/film and my D80.I think I will take a few shots with my nikon film slr and then without moving the tripod I will place the same lens on my D80 then I can print the shots and the difference in angle of view will be apparant.
I would agree with the point that your subject should feel comfortable and a medium telephoto is certainly more likely to achieve this.
I very much want my potraits to look natural and in the right perspective ,it would seem therefore that as long as I steer clear of wideangles most good lenses between 50m and say 135m should produce satisfactory results.