Originally posted by joe.penn
Thanks @jpzk, and yes the 560 is very tasty! I am trying to get my hands on a Pentax 1.7 to put on the 300 to make it 510 to hold me over for a bit, just can't seem to get one for a descent price.
I tried, many, many times the combo DA*300/4 + the much-sought-after Pentax 1.7X TC and I have never been satisfied with the resulting IQ.
From using the DA*300 on its own, with its characteristic wonderful IQ, to using it with that TC: I'd say one out of ten shots would deserve a 8/10 rating (vs. 10/10 most of the time with the lens alone).
That 8/10 rating is when the exposure is perfect, the subject is contrasty and there is no distant haze.
I am waiting for a choice of longer focal and hopefully Pentax will deliver.
Otherwise, the Sigma 500/4.5 would be the best pick ... although very much more expensive probably.
JP