Wow. I'm not sure how I missed this thread until recently, but I almost feel like I've had an epiphany.
A lot of this conversation has revolved around "high end" lenses. But having read this whole thing, including Jonas' post, I feel like I've learned most about my "lowest" end lens, the FA-J 75-300. And Probably how to take best advantage of a very inexpensive lens...
It suddenly made sense to me why it seems to me that the FA-J 75-300 "mis-focuses" so frequently.
The OOF dispersion circles in the FA-J 75-300 is much like "example #1" or even more "example #2" of Jonas' blur dispersion examples nabbed from Ken Rockwell's site, though more like #2. The OOF area itself has "sharp edges" between contrast areas. I'm guessing that this causes the AF's contrast meter to decide the scene/subject is "in focus" and thus the high % of shots where AF is confirmed, but is actually short of "correct" focus.
Personally, especially in the greens, I really like the bokeh of the FA-J 75-300. But it definately has an almost "sharp" bokeh in every other color I can think of, especially highlights. You can see what I mean in this "100% crop" of this picture. It's @ 300mm-f/5.8-1/250s-ISO200, wide open and full zoom. The greens bleed through the wings of the plane in the OOF background. This lens artifact has probably been exacerbated by my over-exposure of the background in this shot:
Green's are nice and soft OOF, but everything else is " fuzzy yet edgy" ... Still OOF, but in a "sharp" kind of way.
I think this explains my "love/hate" relationship with this lens. I've loved it with OOF greens, but been dissappointed by OOF highlights and other contrast areas, and it's tendancy to "mis-autofocus" because of it's sharpish rendering of non-green OOF areas, which isn't so much a problem in and of itself, except it fools the AF entirely too consistantly... Unfortunately the manual focus mechanism is < 270 degrees making MF harder than it could be...
Anyhow, I think I've learned a lot here, love to hear feedback...
Thanks!
-Chris