Originally posted by ehrwien Have you tried taking pics without the filter attached?
Yes - no difference. The castle turret test pics were without filter (and MF in 10 x live view K3-ii), the birds at the feeders with filter, AF. I took a whole suit of pics to get a sense of success rate. The lens did ok, a fairly normally high proportion of rejects due to AF slightly off, motion blur (light was very variable as the sun was on/off due to clouds, shutter speeds 1/200-1/2000) etc. I kept double checking focus in live view, it was pretty on most of the time. That was one of my main concerns when I raised this with the seller, that AF could be significantly affected. In terms of action it isn't, it's fast and doesn't really hunt any more than I would expect. Accuracy however is key....
When I did the AF fine tune I did test pics refocusing first from infinity several times, then from close focus several times, to see if there were differences, there wasn't. On the results focus looked close but tending to front even with max -10 adjustment, see sample test pic, 300mm f4
here ps that crop looks way better in the original, not sure whats happing with uploading...
The lack of iq at 300mm f4 is discernably worst at infinity/distant focus.