Originally posted by bng4bk If my budget is limited, and I want that awesome bokeh, can't I get that beautiful 3D image from a 50mm f1.4 for much less than the 77mm ltd and just crop my KX's 12mp image if I want it to look tighter? Seems like higher res sensors kind of negate the need to get in super tight. Staying further back would negate the facial distortion issues associated with shorter FLs. I'm trying to find a good portrait lens for singles and maybe two or three people and it seems like the 77 would limit that, whereas the 50 gives more flexibility with my subjects.
For looser portraits, the 50 should be fine. Cropping is a great tool and only problematic when you are printing massive copies of your photo. All in all, your question is a little misleading. You should ask yourself whether you NEED the best portrait lens in production. The 50 you already have has lots of potential. I've seen folks on here take stunning portraits with manual focus 50's from the 70s! (Pentax AND off-brand).
Unless you have money to burn, I would say don't spend money unless you see a need. The 50 you have is well regarded by all sorts, and is very sharp at f2. Also, consider that the functional focal length of 75mm is not too far off of the classic portrait length of 85mm, while the 70-77 brings you into 100+ territory. Now the 100 range is useful for all sorts of portraits, sure, but it's not like the 50 is that far off either!
I take back my suggestion for the DA 70. Enjoy THINKING about these lenses as we all do, but be happy in the knowledge that you have very good gear and don't need to spend money to take good photos, because you can always just become a better photographer
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