Originally posted by paulh I've got a few 50's - M and A 50/1.7, and a K55/1.8. Is the 1.4 different enough from these to justify it? (I can guess the answer
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Your guess is correct
I recently picked up the K55/1.8 and I'm keeping it too. The slightly longer FL gives a meaningfully different perspective for portraits, and my impression based on a few shots is that the bokeh & overall rendering has a somewhat different flavor than the M50s.
The M50/1.7 is reputed to have better corner sharpness, while the M50/1.4 has better center sharpness. And no question, the half-stop difference from 1.7 to 1.4 is also significant, particularly for getting that really thin DOF for close subjects.
M50/1.4 remains my favorite of the three, but then I've shot with it the most by far.