I always used my 85mm 1.8 lens for portraits when using a film SLR, but with 20D it was a bit on the long side due to the 1.6 crop. I therefore had to use a shorter lens, namely the 50mm 1.8 with the 20D.
My query is this - I have always understood perspective to remain the same, all you are doing is cropping the image from full frame to 1.6. 'Portrait' lenses are normally said to start at 85mm as you get a more pleasing perspective from the longer lens. But does this mean that by using 50mm 1.8 on a 20D I have been losing out on the more pleasing perspective that one gets from a longer lens?
(I have recently moved to 5D in any event - but I had never realised the significance of the 1.6 crop in this regard until I see the results with 85mm 1.8 on full frame)