With some sunny weather this afternoon, I went out to make a few further shots with K20D, DA*300 and Pentax F 1.7x AF converter.
K20D, 510mm, 1/400s, f/10.0, 400iso
K20D, 510mm, 1/500s, f/10.0, 400iso
K20D, 510mm, 1/500s, f/10.0, 400iso
K20D, 510mm, 1/320s, f/9.0, 400iso
(this shot has just been converted from RAW, no further PP. The shot is available in full resolution on my flickr account, reacheable by clicking on the photo)
The big surprise this afternoon were the bohemian waxwings:
K20D, 510mm, 1/400s, f/8.0, 800iso
K20D, 510mm, 1/400s, f/8.0, 800iso
K20D, 510mm, 1/200s, f/8.0, 800iso
K20D, 510mm, 1/200s, f/8.0, 800iso
I do not know how you see these shots, but I am really satisfied with the results obtained with this combo. The 1.7x TC introduces a slightly reduced sharpness and a little bit of AC, but the end results remains very good.