Originally posted by robgo2 Oh, I was hoping that you would have the definitive answer to my query.
I don't have the money to own all of these lenses at once, and I've only ever played with the FA 43 once. I sold my FA 50 to buy the DA 40, and again sold my DA 40 to buy a FA 50.
However I can tell you a few things about bokeh and sharpness. The DA 40 is very sharp corner to corner, but at pixel peeping levels, it's not as sharp as the FA 43 or 50 stopped down. The DA 40 has some nippley bokeh at f2.8, but nothing too noticeable. In general, the bokeh of the 40 is pretty subtle (due to the focal length and aperture).
The FA 50 has some funny looking bokeh at f1.4, as well (similarly to the FA 43). The 50 is never as sharp as the FA 43, but once again, you would have to be looking very hard to see the difference at f4 - f8. The real difference is between f2 - f4, where the FA 43 is clearly sharper. On the other hand, the FA 50 tends to deal with busy backgrounds in a more pleasing way then the FA 43.
Part of this advantage is due to the speed of the FA 50, which is almost a full stop over the FA 43. So compared at f2, the 50 has a 1 stop advantage of smoothing going on. Another is the focal length... for the same reason the FA 77 beats the pants off of the FA 50. The third is that the FA 50 is not as corrected for sharpness as the FA 43. So the FA 50 is not as sharp (center or corner) as the 43, but it tends to smooth out backgrounds better.
Truth be told, both lenses are compromises. If they cost the same amount, I think people would be more willing to admit this, although I could understand why one would prefer the 43's rendering over the 50. In the end, the truth is that you pay handsomely for the fit and finish of an FA limited. There is no question that manually focusing the 43 is a nicer experience than it is with the 50. IQ differences, however, are more a matter of subjectivity than objective advantages.
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The point, though, is that comparing one lens wide open to another lens stopped down, isn't really that fair. And in this discussion, I noticed the comparisons tended to be done in such a way as to favor the 43, which isn't the point of a comparison.