Originally posted by redpit Pardon me for jumping in this conversation-question but I'm in the happy position of owning both lenses for about 7 months now (since I bought the DA 560). In fact I'm going to post samples and do a short of review about the DA 560 when I find some time. I could also compare the 2 lenses in a later stage too.
The DFA is noticibly faster in acquiring focus and is more reliable in tracking conditions. I'm mostly shooting aviation and then some bird-"wildlife" photography and what I've found is that the DFA is more suitable for most cases and much more versatile as a lens (partly because it's a zoom lens but I'm not reffering to that, but to its performance in general). The DA 560 is a special lens and I love it but it is more difficult to tame and requires extra effort to produce the best results. It's very rewarding too if you know what you're doing and you're having a good photographic day!
An example of what I'm describing is when I tested both lenses in an airport next to the landing strip having fast military jets coming in for landing. The DA 560 was struggling to acquire focus and the success rate was very small in relation to the DFA where almost every frame was tack sharp (mostly @ 450mm - so the distance was not a restrictive factor against the long prime). Those findings were on the K-1. What I'm describing is that if I have to go for a shooting mission and what I'm going to cover is something unique that I would like to have the best success rate I can, I would go for the DFA 150-450. If I have the convenience to have plenty of time or many opportunities to take the shot I want then I would go for the DA 560 to give me that special extra quality of the prime. Usually most situations are a mixed bag of these two "separate" situations and it is up to the user to decide what he is after.
I will come back at some point with samples to back up my findings.
Thanks for your report! It makes sense: focussing on e.g. birds of prey in flight is very hard with the DA560, because it takes too much time to get an initial focus lock, and on top of that, initial focus in such a circumstance is not very reliable. Where the DA560 works best, is in situations where you have the time to re-focus a few times, using the viewfinder to judge if focus is good. That is at least my experience. Quickly aiming and focussing and taking a shot never really works for me. Such opportunities are mostly lost because the DA560 misses spot-on focus. If I have enough time to pamper the focus a bit, the DA560 is very good though.
Also, with the K3(II) I find that I have to take some extra care to ensure that everything is optimal: I blow the AF mirror once or twice every year, I toggle the two switches on the DA560 every now and then to ensure optimal contact. I clean the front of the lens regularly, I clean the contacts on the lens and camera (and 1.4TC) once or twice every year. I keep the battery above half charged if possible. I have found that if I do not do these things, than I have a greater chance of getting a lower keeper rate due to random and sudden inprecise focus. (I shortly tried the KP, and it seemed a far less critical situation with that combo though).
Good to know that newer lenses like the DA150-450 are better at things like initial focus lock. I have come to accept the DA560 for what it is and for its qualities, but I miss opportunities that demand fast focus action, and I am not able to develop BIF skills. So I plan to acquire óne more super telelens during my life of photographic activity. It will be probably a 10.000+ lens and very likely a 500mm f4 (+ 1.4TC for small birds), but knowing that a lens built like the DA560 can be used for 10-20 years without ever failing once, and without deteriorating quality, it is worth it. It will take a few years to finace it, so perhaps Pentax will surprise me with a 500/4....
Chris