The FA 77 is a joy to use, great for portrait, just point it at someone and have a great result (i'm not kidding) ! The 135mm f2 on the other hand is a beast : big, heavy, sharp (super sharp, it's as sharp as the Zeiss 135mm f2 !) and it's manual focus. For the paper thin depth of field, it's really really hard to get it right, for portrait it's the eye, you have the 100mm f2 then you can try manual focus that lens when shooting people for a day, and then imagine you will have to manual focus everyday with the 135mm/2. If you can live with that, then 135mm f2 is considered the best portrait lens at that price range. Personally i will choose the FA77 anytime because it's light, sharp, great color, sweet bokeh and auto-focus (i love AF
) and it's the greatest lens voted on PentaxForum